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IN THE UNITED STATES PATENT AND TRADEMARK OFFICE 



Applicants: J.G. BEDNORZ ET AL. : Date: March 21, 1988 
Filed: 05/22/87 : Serial No.: 06/053,307 

Group Art Unit: 115 : Examiner: Dennis Albrccht 

FOR: NEW SUPERCONDUCTIVE COMPOUNDS HAVING HIGH TRANSITION TEMPERATURE 
AND METHODS FOR THEIR USE AND PREPARA TION 



DECLARA TION OF J. GEORG BEDNORZ AND K.A. MUELLER 
WITH RESPECT TO HIGH Tc SUPERCONDUCTIVITY 



Commissioner of Patents and Trademarks 
Washington, D. C. 20231 

Sir: 

We, J. Georg Bednorz and K.A. Mueller, hereinafter say and declare the following: 



1. We are the inventors of the contribution described and claimed in the subject U.S. patent 
application. This application describes our earlier discovery of high temperature superconductivity in 
ceramic copper oxide materials. In particular, one of the earlier systems in which we worked was 
comprised of Ba-La-Cu-oxides which exhibited superconducting onset temperatures in the mid |^/* 
j^r thirty K range. 

2. We conducted extensive research on these materials to establish their superconductivity in 
our laboratory in Zurich, Switzer- land. This work traced back to early 1986 and was described in a 
publication by us that appeared in Z. Phys. B - Condensed Matter 64, 189-193 (1986). This article 
describes, among other items, resistivity versus temperature measurements that we made on samples of 
this material to show its superconductive behavior. We subsequently submitted for publication and 
had published additional articles describing these high Tc oxide superconductors. 

3. On approximately October 16, 1986, we gave Pravecn Chaudhari (Vice-President, Science at 
the Yorktown Research Laboratory of IBM Corporation) six samples of the high temperature 
superconductive ceramic oxide material that we had described in our aforementioned Z. Physik B. 
publication. Pravecn Chaudhari brought these samples back to the U.S. when he returned after 



visiting with us on or about October 16, 1986. These samples were given to him so that 
experimentation and measurement could be performed on the samples in the United States. We knew 
the individuals (Richard Greene and Chang C. Tsuei) who would be involved in the measurements in 
the United States and discussed the measurements with these individuals in approximately the third 
week of October, 1986. We maintained telephone and computer communications with these 
individuals from that time continually through the remainder of 1986 and into 1987. 

4. It was decided by us that Richard Greene would do specific heat measurements on these 
samples while magnetic measurements would be done by us in our Zurich laboratory. Greene worked 
for Chang Tsuci and discussed with him the nature of the experiments and development activi- tics to 
be performed at the aforementioned Yorktown lab. We provided guidance to Richard Greene and 
Chang Tsuei by describing the nature of these superconducting samples and the types of properties 
that we had measured relative to these samples. One of us (K.A. Mueller) also discussed confirmation 
of our resistivity versus temperature measurements with said Chang Tsuci in a telephone converation 
in October, 1986. 



5. The early work conducted by the individuals in the Yorktown laboratory on our 
superconducting samples occurred with the supervision and guidance that we furnished to these 
Yorktown scientists. Addition-ally, we provided a preprint to Richard Greene of an article that we 
subsequently published in Europhysics Letters 3, (3), pp. 379-385 (1987). This article was given to 
Greene in October, 1986 and described magnetic measurements on these superconducting samples. 

6. We were aware of the work being conducted on our samples at the Yorktown lab and were 
in contact with the individuals there, and particularly Richard Greene, who reported to Chang Tsuei. 
Since the specif-ic heat measurements generally take longer, we had considerable interac-tions with 
Rick Green over a period of time from about October 22, 1986 through December, 1986, concerning 
his specific heat measurements. We also were made aware of Chang Tsuci's measurements of 
resistivity versus temperature of the Ba-La-Cu-oxidc samples, which confirmed our earlier resistivity 
versus temperature measurements. 



7. We further declare that all statements made hereinabove based on our own knowledge arc 
true and that all statements made on information and belief arc believed to be true. We further declare 



that these statements are made with the knowledge that willful false state- mcnts and the like so made 
are punishable by fine or imprisonment, or both, under Section 1001 of Title 18 of the United States 
Code and that such willful false statements may jeopardize the validity of our Patent Application or 
any patent issuing thereon. 




DATE: ^ 
J.tiEOR$f BEDNORZ / 



K.A.MUELLER DATE: 2. 7» /^J<P 



4 



IN THE UNITED STATES PATENT AND TRADEMARK OFFICE 



Applicants: J.G. BEDNORZ ET AL. : Date: March , 1988 

Filed: 05/22/87 ( : Serial No. : 06/053,307 

Group Art Unit: 115 : Examiner: Dennis Albrecht 

FOR: NEW SUPERCONDUCTIVE COMPOUNDS HAVING HIGH TRANSITION TEMPERATURE 

AND METHODS FOR THEIR USE AND PREPARATION 



DECLARATION OF ALEXIS P. MALOZEMOFF 
WITH RESPECT TO HIGH Tc SUPERCONDUCTIVITY 



i Commissioner of Patents and Trademarks 
i Washington, D.C. 20231 

Sir: 

1. Alexis P. Malozemoff, hereby declare and say that: 

I 1. I have a PhD front Stanford University and was a Senior Manager 

j in the Physical Sciences Department at the Thomas J, Watson Research 
Center of IBM Corporation at Yorktown, N.Y. in the fall of 1986. At that 
time, Chang C. Tsuei reported to me while Richard Greene and Sung II Park 
reported to Chang Tsuei. I had general responsibility for a research 
program in superconductivity and amorphous materials. 

2. In approximately September - October 1986, I was made aware of 
the pioneering work in superconductivity done by Bednorz and Mueller in 
Zurich. I had seen an activity report prepared by the Zurich Research 
lab of IBM Corporation, which detailed that work and the measurements 
that Bednorz and Mueller had made on Ba-La-Cu-0 ceramic superconductors. 
In response, I discussed specific heat measurements that could be made on 
these superconducting materials to complement the work being done at 
Zurich by Bednorz and Mueller. My discussion was with Richard Greene 
whom I encouraged to be involved in this technical activity. 

3. On or about November 15, 1986, Richard Greene and I traveled to 
Baltimore for a Magnetism conference. During our travel to Baltimore, we 
discussed Greene's ongoing experiments on high T Q superconducting samples 

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- 2 - 



which he said had been received from Bednorz and Mueller. Specifically, 
we discussed Greene's preliminary data on specific heat measurements. 
Richard Greene reported to me that the diamagnetic signal was present but 
very small. I encouraged him to continue with his measurements with the 
anticipation that he might ( be able to present a paper at the Materials 
Research Society meeting that was scheduled for December, 1986. 

4. I recall Chang Tsuei telling me his measurements of resistivity 
versus temperature on the superconducting samples of Ba-La-Cu-Oxides 
which had been obtained fron Zurich. These measurements were done at the 
aforementioned Research Center and Tsuei reported that his measurements 
confirmed earlier measurements of Bednorz and Mueller and were consistent 
with the results published by Bednorz and Mueller in Z. Phys. B-Condensed 
Matter 64, pp. 189-193 (1986). My recollection of the exact date Chang 
Tsuei told me of his resistivity versus temperature measurements is not 
clear. However, I do know that he told me in either November or December 
of 1986. To the best of my recollection, Tsuei 1 s discussion with me was 
shortly after the Materials Research Society meeting in Boston the first 
week of December, 1986. 

5. I do have a strong recollection of the work of Richard Greene on 
the specific heat measurements -of these samples and of his measurements 
of resistivity versus temperature in the presence of a magnetic field. 
Greened work at the Research Center started soon after he received the 
superconducting samples in October, 1986 and continued on a daily basis 
throughout the remainder of 1986 and into 1987. He discussed with me and 
showed me data concerning these measurements, which indicated to me that 
a portion of the samples was superconducting. During this time he told 
me that he also communicated regularly with Bednorz and Mueller in Zurich 
to inform them of his work and to coordinate his efforts with those of 
Bednorz and Mueller. He said that he received technical guidance and 
support from Bednorz and Mueller and worked in complete collaboration 
with these individuals* 

6. I further declare that all statements made hereinabove are of my 
own knowledge and are true and that all statements made on information 
and belief are believed by me to be true. Further, I declare that these 
statements were made in the knowledge that willful false statements and 
the like so made are punishable by fine or imprisonment, or both, under 



YO987-074 



il 

ii Section 1001 of Title 18 of the United States Code and that such willful 
! false statements may jeopardize the validity of a Patent Application or 
.; any patent issuing thereon. 




YO987-074 



IN THE UNITED STATES PATENT AND TRADEMARK OFFICE 

Applicants: J.G. BEDNORZ ETT AL. : Date: March 29 , 1988 

Filed: 05/22/87 ( . Serial No.: 06/053,307 

Group Art Unit: 115 : Examiner: Dennis Albrecht 

FOR: NEW SUPERCONDUCTIVE COMPOUNDS HAVING HIGH TRANSITION TEMPERATURE, 
AND METHODS FOR THEIR USE AND PREPARATION 

DECLARATION OF CHENG-CHUNG JOHN CHI 
WITH RESPECT TO HIGH Tc SUPERCONDUCTIVITY 

Commissioner of Patents and Trademarks 
Washington, D. C. 20231 

Sir: 

I, Cheng-Chung John Chi, hereby declare and say the following: 

1. I have a PhD in Physics which I received from the Univer- 
sity of Pennsylvania in 1976. After graduation, I did Post-doctoral 
work at the University of California, Berkeley and then joined the 
Research Division of IBM Corporation in 1979. I am presently a research 
staff member on the technical staff of the Director of Research at the 
Thomas J. Watson Research Center of IBM Corporation located at Yorktown, 
New York. 

2. At a time prior to approximately the middle of November, 
1986, Chang C* Tsuei told me of measurements he made on samples of high 
T c superconducting material which he said were received from Georg 
Bednorz and K. A. Mueller, two physicists working for IBM Corporation in 
Zurich, Switzerland. These samples of superconducting material were 
La-Ba-Cu-0 crystalline materials of the type described by Bednorz and 
Mueller in Z. Phys. B-Condensed Matter 64, pp. 189-193 (1986). Chang 
Tsuei said that he had measured resistivity versus temperature of these 
samples • 

3. In the time frame mentioned hereinabove, Chang Tsuei 
showed me plots of resistivity versus temperature for the measurements 
he had made on these superconducting samples. I recall him telling me 
that the superconducting transition was "not really sharp", which is to 



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be expected for samples prepared during the infancy of a technology 
development. I recognized that these plots were evidence of 
superconductivity with high T , even if the transition were not very 
sharp at that time. Based on Tsuei's statements tome, I believe that 
these resistivity versus temperature plots were shown to me within a day 
or two of the time Tsuei made these measurements in his laboratory. 

4. All acts described by me in this declaration occurred in 
the United States. 

5. I further declare that all statements made hereinabove are 
of my own knowledge and are true and that all statements made on infor- 
mation and belief are believed by me to be true. Further, I declare 
that these statements were made with the knowledge that willful false 
statements and the like so made are punishable by fine or imprisonment, 
or both, under Section 1001 of Title 18 of the United States Code and 
that such willful false statements may jeopardize the validity of a 
Patent Application or any patent issuing thereon. 



CHENG-CHUNG JC& CHI 



DATE: 



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; IN THE UNITED STATES PATENT AND TRADEMARK OFFICE 

| 

! 

I Applicants; J.G, BEDNORZ E7T AL. : Date: March 29, 1988 

i 

j Filed: 05/22/87 ^ - Serial No,: 06/053,307 

j Group Art Unit: 115 : Examiner: Dennis Albrecht 

FOR: NEW SUPERCONDUCTIVE COMPOUNDS HAVING HIGH TRANSITION TEMPERATURE, 
AND METHODS FOR THEIR USE AND PREPARATION 

DECLARATION OF SUNG IL PARK 
WITH RESPECT TO HIGH Tc SUPERCONDUCTIVITY 



: ; Conmissioner of Patents and Trademarks 
j Washington, D.C. 20231 

>j Sir: 

■ ! 

; I, Sung II Park, hereby declare and say that: 

| 1. I received a PhD in Applied Physics from Stanford 

! University in October, 1986. I joined the Thomas J. Watson Research 
Center of IBM Corporation in Yorktown, N.Y. on approximately October 20, 
1986, and began work as a Post-doctoral employee. My initial assignment 
was in the areas of Thin Film Interfaces and high T c superconductivity. 
Almost from the beginning of my employment by IBM Corporation I worked 
exclusively on high T, superconductivity and reported to Chang C. Tsuei. 
I am presently working in the same capacity for Chang C. Tsuei, one 
hundred percent of my time being spent on high T Q superconductivity. 

2. I was told by Chang C. Tsuei that superconducting samples 
had been received by Richard Greene, the samples having been brought from 
IBM Corporation's Research Lab in Zurich, Switzerland. These were said 
to be Ba-La-Cu-Oxides that had been fabricated by Georg Bednorz and Alex 
Mueller in Zurich, Switzerland and transported to the U.S. by Praveen 
Chaudhari. Soon after I began working for Chang C. Tsuei, he asked me to 
prepare two of these samples for measurements of resistivity versus 
temperature. To do so, I and Greene cut pieces from these samples to be 
used for the measurements. I then pressed indium dots into these cut 

1 samples to provide electrical contacts. I attached copper wires 

\ YO987-074 



V" 



to the indium dots in order to allow connections to a current source and 
to voltage-measuring equipment. The individual copper wires were given 
number designations to allow them to be properly attached to the 
equipment used for the current and voltage measurements* This numbering 
system is represented by the two figures appearing in Chang C. Tsuei's 
laboratory notebook, a true copy of two pages of which are attached 
hereto and labeled Exhibit A. 

3. In order to determine resistivity versus temperature, 
measurements were made of the current flowing through the Ba-La-Cu-Oxide 
sample while the voltage across two of the copper leads was measured. 
Both positive and negative polarity currents were used in order to avoid 
thermal effects that sometimes occur when making DC measurements. The 
superconducting sample was located on the end of a long probe and placed 
in a dewar containing liquid helium. The temperature was varied by using 
a heater placed near the sample. Data of current and voltage were taken 
from 4. 2K to 5 OK. A germanium thermometer near the sample was used to 
measure the sample temperature. Since resistance is proportional to 
voltage, the voltage and current measurements allowed the resistance (and 
therefore the resistivity for a sample of known dimensions) to be 
measured as a function of temperature. I worked with Chang C. Tsuei to 
take these measurements and used a xy recorder to provide graphical plots 
of resistivity versus temperature for the temperature range 50K-4.2K for 
at least two of these Ba-La-Cu-Oxide samples. 

4. The preparation and measurement of the aforementioned 
superconducting samples occurred at a date prior to November 15, 1986, 
and to the best of my recollection occurred on or about November 9, 1986, 
the date when a helium dewar was pumped down preparatory to taking the 
actual measurements. I believe that while I was assisting Chang C. Tsuei 
and working under his direction, Bradford Orr observed our data and 
graphical plots, and we told him the nature of the superconducting 
samples and the types of measurements that we were making. 

5. My recollection of the dates when the preparation and 
measurement of these samples occurred is vivid to me. My first week of 
employment under Chang C. Tsuei was spent looking for an apartment and, 
upon beginning laboratory work the following week (about October 28, 
1986) , I was instructed by Chang C. Tsuei to immediately measure the 



YO987-074 



aforementioned samples. I cut pieces from these samples using a fine 
■ wire cutter following the direction of Richard Greene, This was done on 
or about October 28, 1986. After this I contacted the samples with 
indium as described above. This technique was very familiar to me as I 
had used indium contacts many times at Stanford University. 
! 6. Both Chang C. Tsuei and I were enthused about our 

' measurement results, as the data showed a superconducting onset 
temperature of about 35K followed by a drop to zero DC resistivity. We 
noted that the transition to zero resistivity was fairly wide, which we 
' expected to be the case for samples that may have been unperfected and 

not of a single phase. In fact, the question of whether multiple phases 
: were present in the material was something that was noted by Tsuei in the 
; aforementioned laboratory notebook, identified as Exhibit A, attached 
i hereto. 

I 7. At this time, I have been unable to locate the actual data 

j and graphical plots of resistivity versus temperature described 
j hereinabove. I believe that this data may have been misplaced or 

inadvertently thrown out during an extensive cleaning of the laboratory. 

However, my memory of the events preparing the samples for measurements, 

performing the measurements and recording the data, and the results 

indicated by that data, are very clear in my mind. 

8. All of the acts described in paragraphs 1-7 above 
occurred in the United States. 

9. I further declare that all statements made hereinabove are 
of my own knowledge and are true and that all statements made on 
information and belief are believed by me to be true. Further, I declare 
that these statements were made with the knowledge that willful false 
statements and the like so made are punishable by fine or imprisonment, 
or both, under Section 1001 of Title 18 of the United States Code and 
that such willful false statements may jeopardize the validity of a 
Patent Application or any patent issuing .thereon. 




^P^T-- DATE: y 3o fa 

CTTM/- TT Ti*TW / 



SUNG IL PARK 



YO987-074 



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No. 06-9504 (S-1870-CM) • 11 IN. x 8^ IN. (28 cm x 21.6 cm) • 50 SHEETS • COLLEGE & MARGIN RULED 



V€RNON McMILLAN. Inc. Elizabeth .ru 07208 



IN THE UNITED STATES PATENT AND TRADEMARK OFFICE 



Applicants: J.G. BEDNORZ ET AL. : Date: March 29, 1988 

Filed: 05/22/87 ^ : Serial No. : 06/053 f 307 

Group Art Unit: 115 - Examiner: Dennis Albrecht 

FOR: NEW SUPERCONDUCTIVE COMPOUNDS HAVING HIGH TRANSITION TEMPERATURE, 
AND METHODS FOR THEIR USE AND PREPARATION 

DECLARATION OF CHANG C. TSUEI 
WITH RESPECT TO HIGH Tc SUPERCONDUCTIVITY 

; . Comnissioner of Patents and Trademarks 
Washington, D.C. 20231 

Sir: 

' j 

1, Chang C. Tsuei, hereby declare and say that: 

,1 1. I have a PhD in Material Science from California Institute 

ij of Technology, and worked approximately eleven years as a student and 
j| faculty member at Cal. Tech, During this time, my research was primarily 
jj on amorphous materials and superconducting materials. I joined the 
ij Thomas J. Watson Research Center of IBM Corporation in Yorktown, N.Y. in 
| 1973 and continued my work on amorphous materials. For several years, I 
jj have been the Manager of a group in the Physical Sciences Department 
i studying amorphous superconductivity and superconductivity of new High T 
superconducting ceramic materials. 

2. On approximately September 13, 1986, I returned from a 
sabbatical at the K. Onnes Laboratory in Holland, Upon my return, I saw 
a copy of an IBM activity report for May - June, 1986, in which the 
"novel research" of J.G. Bednorz and K.A; Mueller was described. These 
individuals were working in the Zurich, Switzerland research laboratory 
of IBM Corporation, and had observed a steep decrease of resistivity in 
sintered samples of Ba-La-Cu-oxides . A true copy of this activity report 

. is attached hereto and labeled Exhibit A. On pasge 2 of the activity 
■\ report the resistivity versus temperature plot is shown in Figure 1 



YO987-074 



!l 

i herein the onset temperature for superconductivity is in the 35K range. 

The data and measurements discussed in the activity report were later 
1 1 published by Bednorz and Mueller in Z. Phys. B-Condensed Matter, 64, pp. 
; 189 - 193 (1986) , a true copy of which is attached and labeled Exhibit B. 

Based on my previous experience in superconductivity, I was very inter- 
im ested in the work of Bednorz and Mueller and discussed this work with' my 

colleague, Richard Greene (who reported to me) . I told Greene to review 

• this activity report and to start a project on high T superconductors of 

c 

i the type described by Bednorz and Mueller. This project was started by 

Richard Greene and others in the group that reported to me, almost 
. immediately. 

3. I called Alex Mueller in Switzerland via telephone to 
request samples of his superconducting material, as well as to discuss 

j the technical area with him. I also sent computer messages to Mueller, 
| but could n °t contact him. After this, early in October, 1986, I ob- 
; tained a copy of the aforementioned Z. Phys. B article by Bednorz and 
i Mueller. 

4, I knew that on approximately October 17, 1986, Praveen 
Chaudhari was in Zurich, Switzerland. I was told that he was given 
samples of the Bednorz and Mueller superconducting copper oxides to bring 
to the U.S. for collaborative work in the United States. I was also told 
that these superconducting samples were delivered to Richard Greene on or 
about October 22, 1986. Shortly after these superconducting samples were 
received, I began work to confirm the existence of high temperature 
superconductivity in these materials and instructed Sung II Park to 
assist me. To do so, small pieces of these samples were cut by Park and 
Greene and were prepared with indium contact dots to which copper wires 
were attached. These copper wires were attached to a source of electri- 
cal current and to voltage-measuring equipment to determine the existence 
of the superconducting state. As the temperature of the sample was 
lowered, resistivity versus temperature plots were then made using 
standard laboratory techniques. The preparation of these samples for 
measurement was done by Sung II Park, who reported to me and who was 
directed by me to do so. 

5. A true copy of the cover sheet and a page of my laboratory 
notebook is attached hereto and labeled Exhibit C. On the second page of 



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;j 



this exhibit, two diagrams illustrate the samples and show the location 
.| of the indium contact dots on the superconducting samples and the number- 
,| ing given to the copper wires attached to these dots. This numbering 
i enabled us to properly connect these wires to a current source and to 
J voltage-measuring equipment. All entries on this notebook page were made 
: by me. The samples are generally designated by their composition, the 
term "BLCO" standing for Ba-La-Cu-Oxide materials. The designation "BLCO 
21 — II," etc. in the box in the right hand comer of this page and the 
designation "BI£0 2 I" in the circle in the middle of the page were the 
; designations on the sample boxes in which the samples were located. I 
: copied these designations directly into my notebook. On the bottom right 
: hand corner of this exhibit, the words "dewar pumped 3x 10~ 5 Torr 
| 11/9/86" is indicated. I made this notation on November 9, 1986 indicat- 
ing that the dewar was being pumped down in order to enable the resistiv- 
ity versus temperature measurements to be made. Because this dewar 
leaked, the actual measurements had to be made within several hours of 
the pump-down. 

6. The individual superconducting samples were attached to a 
long probe and slowly lowered into the liquid helium dewar while a 
current was passed through the sample and the voltage across two of the 
terminals measured. Sung II Park assisted me. These measurements were 
recorded directly on an xy recorder which plotted resistivity versus 
temperature for these superconducting samples. These plots indicated an 
onset of superconductivity at about approximately 35K, and confirmed the 
results of Bednorz and Mueller in Switzerland. As an example, referring 
to the sample BI£0 2 having connecting wires 20, 21, 22 and 8, electrical 
current was applied between wires 20 and 8, while voltage measurements 
were made across the sample using contact terminals 21 and 22. Since the 
voltage is a function of the resistance of the material, by making the 
voltage measurements at constant currents, resistivity versus temperature 
plots can be developed, These resistivity versus temperature plots 
appear to be missing at this time. I believe that they may have been 
inadvertently thrown away when the laboratory was subsequently exten- 
sively cleaned. 

7. During my measurement of the superconducting samples 
described hereinabove, Bradford G. Orr, who was a Post-doctoral employee 



YO987-074 



I at the Research Center, came into ray lab and observed these measurements, 
as did Albert M. Torressen. These measurements confirmed the high 

| temperature superconductivity of these materials and I was enthusiastic 
about the results. I expressed my enthusiasm to Richard Greene, who was 

■ l anxious to do specific heat measurements on these samples. Subsequent to 
; my confirmation of their resistivity versus temperature measurements, .1 

contacted Mueller in Zurich to inform him of my successful resistivity 
versus temperature measurements. In addition, I told several people 
about my laboratory measurements, including Arthur Williams, Alex 
Malozemoff , Paul Horn, and Praveen Chaudhari, all of whom work in the 
Thomas J. Watson Research Center, 
i 8. From the time we received the superconducting samples in 

. October, 1986 to the present, I, Richard Greene and Sung II Park have 

worked on a daily basis to further explore and develop this technology, 
.j In particular, I observed Greene working on a daily basis to conduct 
,i specific heat measurements during November and December, 1986. 
; 9. All acts described hereinabove relating to sample prepara- 

■; tion, measurement and discussions of these measurements occurred in the 

■ United States. 

10. I further declare that all statements made hereinabove are 
, of my own knowledge and are true and that all statements made on informa- 
j tion and belief are believed by me to be true. Further, I declare that 
j these statements were made with the knowledge that willful false state- 
!j ments and the like so made are punishable by fine or imprisonment, or 
j both, under Section 1001 of Title 18 of the United States Code and that 
| such willful false statements may jeopardize the validity of a Patent 
Application or any patent issuing thereon. 



CHANG C. TSUEI 



DATE: 5/So/$fr 



: i 
i 

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BFgJfg 



ACTIVITY REPORT 
MAY-JUNE, 1986 



Cj _ o I / - 4 / / ' 



Zurich Research Laboratory 
8803 Buachlikon, Switzerland 
5 Ulej^e^h V 724 81 11 
Teleprinter: ITPS CODE ZRL 



MATERIAL SCIENCE T. Schneider, Mgr. 

SURFACE & MATERIAL SCIENCES E. Courtens, Mgr., Project 4181 



August 15, 1986 

\y_00k\ tUf 0 | COMMENTS f flltj 

RfC'D.SEP 03 1365 



Novel Research 



Possible I Iigh-T t Superconductivity in the Ba-La-Cu-O System 
J.G. Bednorz and K.A. Muller (Project 4196) 

We observed a steep decrease of resistivity in sintered Ba-La-Cu-oxide samples, with the highest 
temperature of the onset in the 35 K range (Fig. 1). 

The Ba-La-Cu-O system exhibits a number of oxygen deficient phases with perovskite-like 
layer-type structures. These are characterized by mixed-valent copper ions <Cu 2+ and Cu 3 + ) and 
itinerant electronic states. In addition one expects polaron formation induced by the strong 
Jahn-Teller effect of Cu 2+ In an octahedral oxygen environment. Thus our Ba-La-Cu-O system 
was anticipated to have considerable electron-phonon coupling and metallic conductivity. 

Compounds with the composition Ba(x)La(5-x)Cu(5)0(5[3-y]) have been prepared in 
polycrystalline form. Samples with x < 0.2 and y > 0, annealed below 900°C under reducing 
conditions, consist of three phases, one of them a perovskite-like mixed-valent copper compound 
with K 2 NiF 4 type structure. Upon cooling, the samples show a linear decrease in resistivity, then 
an approximately logarithmic increase, interpreted as a beginning of localization Finally a steep 
decrease by up to three orders of magnitude occurs, reminiscent of the onset of percolative 
superconductivity. The highest onset temperature is observed in the 35 K range. It is markedly 
reduced by high current densities (Fig. 1). The slow sensitivity decay towards low temperatures 
might possibly result from 2D superconducting fluctuations of perovskite layers of one of the 
phases present. 



inM CONriDI-NTIAI. 



ACTIVITY REPORT 



PHYSICS 



MAY-JUNE 1986 -2- 



0.010 



0.008 



• ■• • • • * .4 



0.006 



E 

u 

c: 



0.004 



0.002 - 



o 7.5 A/cm 2 
« 2.5 A/cm 2 
• 0.5 A /cm 2 



>- 
ID 



0.4 0.2 0 0.2 0.4 06 Oj 
WAVE VECTOR (A* 1 ) 



FIG. 1 




X - — = s- /.il c 

|06C 



FIG. 2 



IBM CONFIDENTIAL 



Z. Phys. B - Condensed Matter 64, 189-193 (1986) COndCPlSCd 



SftSSe "Matter 

@ Springer- Verlag 1986 



Possible High T c Superconductivity 
in the Ba - La - Cu - O System 



J.G. Bednorz and K.A. Muller 

IBM Zurich Research Laboratory, Ruschlikon, Switzerland 
Received April 17, 1986 

Metallic oxygen-deficient compounds in the Ba-La-Cu-O system, with the composi- 
tion Ba,La 5x Cu 5 0 5(3 _ y) have been prepared in polycrystalhne form. Samples with 
x=l and 0.75 j»0, annealed below 900 *C under reducing conditions, consisi of three 
phases, one of them a perovskite-hke mixed-valent copper compound. Upon cooling 
the samples show a linear decrease in resistivity, then an approximately logarithmic 
increase, interpreted as a beginning of localization. Finally an abrupt decrease by up 
to three orders of magnitude occurs, reminiscent of the onset of percolative superconduc- 
tivity. The highest onset temperature is observed in the 30 K range. It is markedly 
reduced by high current densities. Thus, it results partially from the percolative nature 
bute possibly also from 2D superconducting fluctuations of double perovskite layers 
oi one of the phases present. 



I. Introduction 

"At the extreme forefront of research in supercon- 
ductivity is the empirical search for new materials" 
[1]. Transition-metal alloy compounds of A 15 
(Nb 3 Sn) and B 1- (NbN) structure have so far shown 
the highest superconducting transition temperatures. 
Among many A 15 compounds, careful optimization 
of Nb-Ge thin films near the stoichiometric compo- 
sition of Nb 3 Ge by Gavalev et aL and Testardi et aK 
a decade ago allowed them to reach the highest T c = 
23.3 fC reported until now [2, 3]. The heavy Fermion 
systems with low Fermi energy, newly discovered, are 
not expected to reach very high r c *s [4], 

Only a small number of oxides is known to exhibit 
superconductivity. High-temperature superconduc- 
tivity in the Li-Ti-O system with onsets as high 
as 13.7 K was reported by Johnston et ai. [5]. Their 
x-ray analysis revealed the presence of three different 
crysiallographic phases, one of them, with a spinel 
structure, showing the high T c [5]. Other oxides like 
perovskites exhibit superconductivity despite (heir 
small carrier concentrations. ?i. In Nb-doped SrTiOj, 
with n = 2 x 10 2 " cm" 2 , the plasma edge is below the 
highest optical phonon. which is therefore unshielded 



[6]. This large electron-phonon coupling allows a T e 
of 0.7 K [7] with Cooper pairing. The occurrence of 
high electron-phonon coupling in another metallic 
oxide, also a perovskite, became evident with the dis- 
covery of superconductivity in the mixed-valent com- 
pound BaPbj _JBi x 0 3 by Sleight et ah, also a decade 
ago [8]. The highest T c in homogeneous oxygen-defi- 
cient mixed crystals is 13 K with a comparatively low 
concentration of carries n = 2~4x 10 21 cm" 3 [9]. Flat 
electronic bands and a strong breathing mode with 
a phonon feature near 100 cm" 1 , whose intensity is 
proportional to T„ exist [10]. This last example indi- 
cates that within the BCS mechanism, one may find 
still higher T c "s in perovskite-type or related metallic 
oxides, if the electron-phonon interactions and the 
carrier densities at the Fermi level can be enhanced 
further. 

Strong electron-phonon interactions in oxides 
can occur owing to polaron formation as well as in 
mixed-valent systems. A superconductivity (metallic) 
to bipolaronic (insulator) transition phase diagram 
was proposed theoretically by Chakravcrty (llj. A 
mechanism for polaron formation is the Jahn-Tcller 
effect, as studied by Hock et al. [12]. Isolated I : e 4 \ 
Ni * and Cu** in octahedral oxygen environment 



J.G. Bednorzand K.A. Muller: Ba-La-Cu-O Systci 



show strong Jahn-Telier (J.T.) effects [13]. While 
SrFe(VI)0 3 is distorted perovskite insulator, 
LaNi(III)0 3 is a J.T. undistorted metal in which the 
transfer energy b n of the J.T. e t electrons is sufficiently 
large [14] to quench the J.T. distortion. In analogy 
to Chakraverty's phase diagram, a J.T.-type polaron 
formation may therefore be expected at the border- 
line of the metal-insulator transition in mixed perovs- 
kites, a subject on which we have recently carried 
out a series of investigations [15]. Here, we report 
on the synthesis and electrical measurements of com- 
pounds within the Ba - La -Cu-O system. This sys- 
tem exhibits a number of oxygen-deficient phases 
with mixed-valent copper constituents [16], i.e., with 
itinerant electronic states between the nbn-J.T. Cu 3 + 
and the J.T. Cu 2+ ions, and thus was expected to 
have considerable electro n-phonon coupling and me- 
tallic conductivity. 



II. Experimental 

/, Sample Preparation and Characterization 

Samples were prepared by a coprecipitation method 
from aqueous solutions [17] of Ba-, La- and Cu-ni- 
trate (SPECPURE JMC) in their appropriate ratios. 
When added to an aqueous solution of oxalic acid 
as the precipitant, an intimate mixture of the corre- 
sponding oxalates was formed. The decomposition 
of the precipitate and the solid-state reaction were 
performed by heating at 900 °C for 5 h. The product 
was pressed into pellets at 4 kbar, and reheated to 
900 °C for sintering. 



2. X-Ray Analysis 

X-ray powder diffractograms (System D 500 SIE- 
MENS) revealed three individual crystallographic 
phases. Within a range of 10° to 80° (20), 17 lines 
could be identified to correspond to a layer-type per- 
ovskite-like phase, related to the K 2 NiF* structure 
(« = 3.79 A and c= 13.21 A) [16]. The second phase 
is most probably a cubic one, whose presence depends 
on the Ba concentration, as the line intensity de- 
creases for smaller A-(Ba). The amount of the "third 
phase (volume fraction > 30% from the x-ray intensi- 
ties) seems to be independent of the starting composi- 
tion, and shows thermal stability up to 1.000 °C. For 
higher temperatures, this phase disappears progres- 
sively, giving rise to the formation of an oxygen-defi- 
cient perovskite <La 3 Ba.,Cu h O^} as described bv Mi- 
chel and Ravcau [16j. 



X - 



oLi L 



• 0.25 A/cm ? 

• 0.50 A/cm 2 
■ 0.50 A /cm 2 



T IK) 



200 



300 



Fig. 1. Temperature dependence of resistivity in Ba.La 5 _,Cu 3 O s (3 _ 
for samples with ,v(Ba)= 1 (upper curves, left scale) and r<Ba) = 
0.75 (lower curve, right scale). The first two cases also show the 
influence of current density 



3. Conductivity Measurements 

The dc conductivity was measured by the four-point 
method. Rectangular-shaped samples, cut from the 
sintered pellets, were provided with gold electrodes 
and contacted by In wires. Our measurements be- 
tween 300 and 4.2 K were performed in a continuous- 
flow cryostat (Leybold-Hereaus) incorporated in a 
computer-controlled (IBM-PC) fully-automatic sys- 
tem for temperature variation, data acquisition and 
processing. 

For samples with *(Ba)<1.0, the conductivity 
measurements, involving typical current densities of 

0. 5 A/cm 1 , generally exhibit a high-temperature me- 
tallic behaviour with an increase in resistivity at low 
temperatures (Fig. 1). At still lower temperatures, a 
sharp drop in resistivity (>90%) occurs, which for 
higher currents becomes partially suppressed (Fig. I ; 
upper curves, left scale). This characteristic drop has 
been studied as a function of annealing conditions, 

1. e., temperature and O, partial pressure {Fig. 2). For 
samples annealed in air. the transition from itinerant 
to localized behaviour, as indicated bv ihe minimum 
in resistivity in the 80 K range, is not very pro- 
nounced. Annealing in a slightly reducing atmo- 
sphere, however, leads to an increase m resisiiviiy 
and a more pronounced localization effect. At the 
same time, the onset of the resistivity drop is shifted 



J.G. Bednorz and fC.A. Muller: Ba-La-Cu-O Syst< 



191 





900 *C 


2h 


® 


540 *C 


15 min 




630 *C 


12 h 


© 


900 a C 


15 min 




900 *C 


1h 




950 *C 


in 


® 


1040°C 


15 min 



0.010 




towards the 30 K region. Curves © and ®, recorded 
for samples treated at 900 °C, show the occurrence 
of a shoulder at still lower temperature, more pro- 
nounced in curve ®. At annealing temperatures of 
1,040 °C, the highly conducting phase has almost 
vanished. As mentioned in the Introduction, the 
mixed- valent state of copper is of importance for elec- 
tron-phonon coupling. Therefore, the concentration 
of electrons was varied by the Ba/La ratio. A typical 
curve for a sample with a lower Ba concentration 
of 0.75 is shown in Fig. 1 (right scale). Its resistivity 
decreases by at least three orders of magnitude, giving 
evidence for the bulk being superconducting below 
13 K with an onset around 35 K, as shown in Fig. 3, 
on an expanded temperature scale. The latter figure 
also shows the influence of the current density, typical 
for granular compounds. 



Ml. Discussion 

The resistivity behaviour of our samples. Fig. 1, 
is qualitatively very similar to the one reported in 
the Li — Ti — O system, and m superconducting 



BaPb 1 . I Bi JC 0 3 polycrystaliine thin films [5, 18]. 
Upon cooling from room temperature, the latter ex- 
hibit a nearly linear metallic decrease of p(T\ then 
a logarithmic type of increase, before undergoing the 
transition to superconductivity. One could, of course, 
speculate that in our samples a metal-to-metal struc- 
tural phase transition occurs in one of the phases. 
The shift in the drop in p(T) with increasing current 
density (Fig. 3), however, would be hard to explain 
with such an assumption, while it supports our inter- 
pretation that we observe the onset of superconducti- 
vity of percolative nature, as discussed below. In 
BaPb, _ x Bi JC 0 3l the onset of superconductivity has 
been taken at the resistivity peak [18]. This assump- 
tion appears to be valid in percolative systems, i.e., 
in the thin films [18] consisting of polycrystals with 
grain boundaries, or when different crystalline phases 
with interpenetrating grains are present, as found in 
the Li - Ti - O [5] or in our Ba - La - Cu - O system. 
The onset can also be due to fluctuations in the super- 
conducting wave functions. We assume one of the 
Ba-La-Cu-O phases exhibits this behaviour. 
Therefore, under the above premises, the peak in /;(7~) 
at 35 K. observed for an ,v(Ba) = 0.75 (Fig. n. has 



192 



to be identified as the start to superconductive coop- 
erative phenomena in the isolated grains. It should 
be noted that in granular AI, Cooper pairs in coupled 
grains have been shown to exist already at a point 
where p{T) upon cooling has decreased by only 20% 
of its highest value. This has been proven qualitative- 
ly [19] and more recently also quantitatively [20] by 
the negative frequency shift occurring in a microwave 
cavity. In 100 A films, a shoulder in the frequency 
shift owing to 2D fluctuations was observed above 
the T c of the grains. In our Ba-La-Cu-O system, 
a series of layer-like phases with considerable variety 
in compositions are known to exist [16, 21], and 
therefore 2D correlations can be present. 

The granularity of our system caj be justified 
from the structural information, and more quantita- 
tively from the normal conductivity behaviour. From 
the former, we know that more than one phase is 
present and the question arises how large are the 
grains. This can be inferred from the logarithmic 
fingerprint in resistivity. Such logarithmic increases 
are usually associated with beginning of localization. 
A most recent example is the Anderson transition 
in granular Sn films [22]. Common for the granular 
Sn and our samples is also the resistivity at 300 K 
lying in the range of 0.06 to 0.02 Hem, which is near 
the microscopic critical resistivity of /? f = 10 L Q hje 2 
for localization. From the latter formula, an inter- 
atomic distance L 0 in the range of 100 A is computed, 
thus a size of superconducting grains of this order 
of magnitude must be present. Upon cooling below 
T cy Josephson junctions between the grains phase- 
lock progressively [23] and the bulk resistivity gradu- 
ally drops to zero by three orders of magnitude, for 
sample 2 (Fig. 1). At larger current densities/ the 
weaker Josephson junctions switch to normal resistiv- 
ity, resulting in a temperature shift of the drop, as 
shown in Fig. 3. The plateau in resistivity occurring 
below the 80% drop (Fig. J) for the higher current 
density of 0.5 A/cm 2 , and Fig. 2 curve ©) may be 
ascribed to switching of junctions to the normal state. 

The way the samples have been prepared seems 
to be of crucial importance: Michel et al. [21] ob- 
tained a single-phase perovskite by mixing the oxides 
of La and Cu and BaC0 3 in an appropriate ratio 
and subsequent annealing at 1,000 °C in air. We also 
applied this annealing condition to one of our sam- 
ples, obtained by the decomposition of the corre- 
sponding oxalates, and found no superconductivity. 
Thus, the preparation from the oxalates and anneal- 
ing below 950 °C arc necessary to obtain a non-per- 
ovskite-type phase with a limited temperature ranee 
ot stability exhibiting this new behaviour. The forma- 
tion of this phase at comparatively low temperatures 
is favoured by the intimate mixture of the compo- 



J.G. Bcdnorzand K.A. Mullcr: Ba - La -Cu-0 System 

nents and the high reactivity of the oxalates owing 
to the evolution of large amounts of H 2 0 and CO 
during decomposition. 2 



IV. Conclusion 

In the concentration range investigated, compounds 
of the Ba-La-Cu-O system are metallic at hieh 
temperatures, and exhibit a tendency towards local- 
ization upon cooling. Samples annealed near 900 °C 
under reducing conditions show features associated 

Tn l £ a " ° nSCt ° f eranular ^conductivity near 
30 K. The system consists of three phases, one of 
them having a metallic perovskite- type layer-like 
structure. The characterization of the new, apparently 
superconducting, phase is in progress. An identifica- 
tion of that phase may allow growing of single crys- 
tals for studying the Meissner effect, and collecting 
specific-heat data to prove the presence of high T 
bulk superconductivity. c 

The authors would like to thank H E. Weibel for his help in gating 
fam.har w,th the conduct.vity measurement system, E Courtens 
and H. Thomas for discussions and a critical reading of the manu- 



References 

l.Tinkham, M., Beasiey, MR., Larbalesticr, D.C Clark AF 
Fmncmore, D.K.: Workshop on Problems in Superconductiv- 
ity, Copper Mountain. Colorado, August 1983 p 12 

I' S?? Cy \ M ^' Geb3lIe ' T H ' : Phys - TodaiSfrili). 60 (1984) 

3. Mullcr, J. : Rep. Prog. Phys. 43, 663 (1980) 

4. On, H.R.: Unconventional Superconductivity. Zurich Phys 
Soc. Seminar. Zurich, February 13 1986 

5. Johnston D-C, Praicash. H., Zachariasen. W.H., Viswanathan, 
R.: Mat. Res. Bull. 8. 777 (1973) 

6^BaratofT, A., Binnig, G.; Physics 108 B, 1335 (1981) 

Baratofr, A.. Binnig. G., Bednorz, J.G.. Gervais. F„ Servoin, 
J-L.: In: Superconductivity in d- and /-Band Metals, Proceed- 
ings IV Conference in 'Superconductivity in d- and /-Band Met- 
als*. Bucket. W. and Weber. W. (cds). p. 419. Kernforschungs- 
zentrum Karlsruhe 1982 

7. Binnig, G., Baratofr A., H5nig. HE.. Bcdnorz. J.G. : Phys Rev 
Lett. 45. 1352(1980) 

8. Sleigh:, A.W., Gillson. J.L.. Bicrsccdi. F.E.: Solid State Com- 
mun. 17. 21 (1975) 

Bailogg. B. : Physica 126 B. 275 < l'JX4) 

,n IT 3 "?* T °" K ° ma ' A " Tuna ^' S : A PP'- !, hvs. 22. 205 (19S0) 

10. Matthcis. F...Hamann. D.R.: p| lvs . Rev (i ift -MO t\W\- 
ibid. 28. 4227 < 19S3) " ' " " 

11. Chakravony. B.K.: J. Phys. Leu. 4(1. L-JO (1979) j Phvs 4 *> 
1351 < 19SI) 

12. Hocfc. K.-H.. Nickoch. H.. Thomas. U _ Uelv. Pnvs . AcU) 56. 
237(1910) 

13. Ungmiann. R. : In: The J.,hn- Teller l:|V, vt in Macules .Mid 
Crysials. London. Neu York. W.icv Imersciencc 1972 

14 Uoodenoueh. j.B.. Una,. M. : M ;i , nctlc ;jmJ olncr proptfrlics 
ot oxide ;md related compounds | n: Land.iH-Uoernstein New 



J.G. Bednorz and ICA. Muller: I 



-La^Cu-O System 



Scries. Vol III/4a: Crystal and solid state physics Hellwegc ^ 
K.H., Hetlwcge, A.M. (eds). p. 262, Fig. 73. Berlin, Heidelberg' ^ 
New York: Springer-Verlag 1970 

15. Bednorz, J.G., Muller, K.A.; (in preparation) 

16. Michel, C. Raveau, B.: Chim. -Min. 21, 407 (1984) 

17. Bednorz, J.G.. Muller, K.A., Arcnd, H., Granicher H Mat 
Res. BulL 18 (2), 181 (1983) 

18. Suzuki, M. ( Murakami, T., Inamura, T: Shinku 24, 67 (1981) 
(in Japanese) 

Enomoto, Y., Suzuki, M., Murakami, T.. Inukai, T., Inamura 
T.: Jpn. J. Appl. Phys. 20, L661 (1981) 

19. Mullcr. K.A., Pomerantx, M„ Knoedler, CM., Abraham D ■ 
Phys. Rev. Lett. 45, 832 (1980) 

20. Stocker, E.. Buttat, J.: Solid State Commun. 53, 915 (1985) 



193 

2 - 0985) 1 * C ' Er " Rakh0 * L ' Raveau * B : MaI Res. BulL 20, 667 

22. Van Haesendonck, C, Bruynscraede, Y. : Phys. Rev. B 33, 1684 
( 1 986) 

23. Deutscher, G., Entin Wohiman, O., Fishman, S., Shapira Y 
Phys. Rev. B 21, 5041 (1980) ' " 



J.G. Bednorz 
K.A. Muller 

IBM Zurich Research Laboratory 
Saumerstrasse 4" 
CH-8803 Ruschltkon 
Switzerland 



Note Added in Proof 

Chemical unalv,,s of the bulk composition of our samples reeled 
dcvKU.on trom the ideal La Ba ratios of 4 and S.ftft.- I he actual 
rauos arc 16 and IS. respectively. This is ,n agreement Wllh an 
identification ol the ihird phase as CuO 




V€RNON McMILLAN, Inc, euzasethmji 07208 



fr '7 ,? 



A 2. 

ft ^J. 



i- Gu 




■] 

•I 
: ! 

1 IN THE UNITED STATES PATENT AND TRADEMARK OFFICE 

t 

\ Applicants: J.G. BEDNORZ ET AL. ; Date: March 29, 1988 

,; Filed: 05/22/87 : Serial No.: 06/053,307 

; Group Art Unit: 115 : Examiner: Dennis Albrecht 

FOR: NEW SUPERCONDUCTIVE COMPOUNDS HAVING HIGH TRANSITION TEMPERATURE 
AND METHODS FOR THEIR USE AND PREPARATION ' 



DECLARATION OF RICHARD L. GREENE 
WITH RESPECT TO HIGH Tc SUPERCONDUCTIVITY 



;j Ccmnissioner of Patents and Trademarks 
I; Washington, D.C. 20231 

■I Sir: 

I 



ij I, Richard L. Greene, hereby declare and say that: 

i 1. I received a Ph. D in physics from Stanford University in 

:; 1967, and joined the San Jose, California laboratory of the Research 
I Division of International Business Machines Corp. in 1970. I was the 
|j Manager of a group conducting research on organic superconductors and 
j; have worked in the field of superconductivity for 20 years. I 

transferred to IBM Corp. research laboratory in Yorktown, New York, in 
July 1986, and continued thereafter to conduct research on 
superconductive materials. From about October 1986 to the present I have 
worked on high T, superconducting oxides. 

2. At approximately the end of September - first week of 
October, 1986, my manager, Chang C. Tsuei, showed me a copy of an activity 
report from the Zurich Research Laboroatory of IBM Corporation. This 
activity report described the work of J.G. Bednorz and K.A. Mueller and 
their discovery of new superconducting compositions. These materials 
were mixed copper oxide ceramics that exhibited an onset of 
superconductivity at a temperature significantly higher than the 
transition temperatures reported for previously known superconductors. 
Materials of this general class are now known in the art as high T 



YO987-074 




superconductors. A true copy of this activity report is attached hereto 
j and labeled Exhibit A. 

;] 3. Soon after reading this activity report and discussing it 

| with Chang C. Tsuei, I called K.A. Mueller in Zurich and requested 
; samples from him so that I could make measurements on these samples in 
\ the United States. This telephone call occurred approximately October 1 
I ~ October 6, 1986. My intent was to begin a research project on these 
• materials, as I was very interested in them based on my previous work in 
; superconductivity. My plan at that time was to do experiments which 
would be complementary to those being conducted by Bednorz and Mueller in 
Zurich, so that a maximum amount of information could be obtained about 
; these new superconducting materials. Based on the data in this activity 
; report and on the results of susceptibility measurements described to me 
■ by Alex Mueller in the aforementioned telephone call, I believed that a 
j new class of superconducting materials with T q greater than 30K had been 

t discovered. 

i 

j 4. In approximately mid-October, 1986, Praveen Chaudhari, 

i Vice-President, Science, at IBM's Watson Research Laboratory visited the 
| Zurich IBM Lab. Based on my request for samples of the new 
superconducting material, Chaudhari told me that he had obtained them 
from Bednorz and Mueller and brought them back to the United States with 
hjjiu These were about six samples in the Ba-La-Cu-0 system. Chaudhari 
returned to the United States on or about October 20, 1986 and delivered 
these samples to me. Of these approximately six samples, they varied in 
the different amounts of La and Ba that were present. Oily two of the 
samples were reported as being single phase materials. 

5, Immediately upon receiving these samples, I was in contact 
with Bednorz and Mueller, via telephone and computer system links, in 
order to discuss with Bednorz and Mueller the experiments that I would 
conduct and also to obtain information from Bednorz and Mueller relative 
to the characteristics of the samples. I had planned to do specific heat 
measurements of the samples and also resisitivity versus temperature 
measurements in the presence of a magnetic field. Because of the 
importance that I attributed to this work, I worked substantially full 
time on these superconductor materials in order to further characterize 
them. My first specific heat measurements occurred approximately October 
29 and 30, 1986, while I measured resistivity versus temperature in the 
! YO987-074 



i 



! presence of a magnetic field in late November, 1986. Continuously 
: throughout the period, October 20, 1986 - February, 1987, I worked on a 
:j daily basis to further characterize these materials. At all times, I was 
| in contact with Bednorz and Mueller, exchanged data with them, and worked 
: in close cooperation with tjiem. They provided information to me about 
1 the characteristics of the material, as well as providing me up-to-date 
: information concerning the data they had obtained about these materials. 

A true copy of my computer log from October, 1986 - January 12, 1987 is 
' attached hereto and labeled Exhibit B. Excerpts which do not relate to 
■ superconductivity have been deleted. In this exhibit, the identifier for 
: K.A. Mueller is "KAM" , while the identifier for J. G. Bednorz is "BED". 

Bednorz and Mueller are located in Zurich, Switzerland and the computer 
j node for them is ZURLVM1. My identifier is "RGREENE" . This computer log 
j details my ongoing computer dialogue with Bednorz and Mueller relative to 
| theirs and my activities on the high T superconductor materials. In 
| addition to this computer correspondence, I also talked with Bednorz and 
| Mueller via telephone. 

6. During my specific heat measurements of these materials, 
as well as the measurements of resisitivity versus temperature in the 
presence of a magnetic field, I was assisted by Albert M. Torressen, who 
was a laboratory specialist. I also discussed my laboratory experiments 
with Chang C. Tsuei, s. von Molnar, Merril W. Shafer, Sung II Park, 
Thomas Penney, and Arthur R. Williams. 

7. The specific details of the apparatus and the data 
obtained in the specific heat measurements will be described in a 
separate statement by Albert M. Torressen, the laboratory specialist who 
worked with me to provide these measurements. Essentially, the specific 
heat of the apparatus was calculated to provide calibration and 
background specific heat, after which the sample was introduced into the 
apparatus and the total specific heat again measured. By subtracting the 
background specific heat, the specific heat of the superconducting sample 
is determined. This was done over a temperature range of approximately 
2-50K. 

8. The specific heat measurements of these superconducting 
samples were begun approximately October 21, 1986, and were conducted on 
a daily basis by me and Al Torressen through November and December, 1986. 



YO987-074 



: 1 

; These specific heat measurements and the curves which were plotted are 

■ representative of these superconducting materials, and are also 

■ representative of the specific heat versus temperature plots obtained on 
t present samples of superconducting high T c oxides, 

1 1 9, In addition to the specific heat measurements described 

hereinabove and in the accompanying statement of Albert M. Torressen, I 
' also performed measurements of resistivity versus temperature in the 
i presence of a magnetic field, for the samples of Ba-La-Cu-0 obtained from 
I Bednorz and Mueller. The specific heat measurements were performed first 
: on these samples, after which I measured resistivity versus temperature 
;; in an applied magentic field, in order to further characterize these 
m samples. These resistivity measurements were done at the end of 
:j November, 1986, and the beginning of December, 1986. Exhibit C is a true 
;j copy of nine pages of my data notebook, together with a copy of the cover 
! | of this notebook entitled "Zurich oxide BLCO DATA (T,H). H The date 
jj "11/15/86" is also on the cover. Exhibit D is comprised of several pages 
: ; of plots of resistivity versus temperature for these superconductor 
| samples, as well as resistivity as a function of magnetic field at 
i particular temperatures. In some instances, the Ru0 2 sample holder is 
! taken into account into the plots. Generally, these plots represent the 
graphical expressions of the data contained in Exhibit C. Exhibit E is a 
composite plot incorporating the different plots found in Exhibit C, and 
shows resistivity versus temperature for different values of applied 
magnetic field. I used this composite plot at a seminar that I gave to 
other researchers at the Yorktown lab on December 12, 1986. 

10. In order to obtain the data listed in Exhibit C, I used a 
laboratory belonging to Stephan von Molnar. Albert M. Torressen, who 
reported to von Molnar, showed me the necessary equipment to make these 
measurements, and I preceded to make them on my own. However, many 
people were aware of these resistivity measurements and viewed the data, 
including both Thomas Penney and Albert Torressen. In addition, Thomas 
Penney observed me making these measurements and understood the procedure 
and nature of my laboratory work. 

11* I have numbered the data pages of Exhibit C in red in the 
upper right hand comer. Page 1 describes the sample set-up that I used 
for these measurements and the background data in order to ready the 

;j YO987-074 



apparatus for the resistivity versus temperature measurements. This 
sample was the BtCO -21 II, standing for Ba-La-Cu-Qxide material. Page 2 
shows two views of the experimental apparatus and the calibration 
measurements made between particular terminals. The wires A, B, C and F 
: are those which are also shown on page 1 . 

12, On pages 3, 4, and 5 I had listed the data that applied 
to the Ru0 2 sample holder and the four point probe. The sample was 
contacted with indium contacts and copper wires were attached to the 
indium contacts for the measurements. Both DC and AC measurements were 
made. The resistance of the sample is R^. which was measured at various 
temperatures with the applied magnetic field H equal to zero (page 4) . 
Pages 5-9 show further measurements that were made at different 
temperature settings and applied magnetic fields. All of the data on 
these pages were taken by me and entered by me in this notebook. 
; 13. The plot of resistance versus temperature in exhibit D is 

; a plot for the data which was obtained December 3 - December 5, 1986. 
'; Referring to Exhibit D, this plot shows the superconducting transition 
• that begins to occur about 35K, where the transition shifts to the left 
: in the presence of a magnetic field. This is an indication of a 
; superconductor. 

14. All acts performed by me as described hereinabove 
occurred In the United States, 



1 1 15. I further declare that all statements made hereinabove 

on 



are of my own knowledge and are true and that all statements made „. 
information and belief are believed by me to be true. Further, I declare 
that these statements were made with the knowledge that willful false 
statements and the like so made are punishable by fine or imprisonment, 
or both, under Section 1001 of Title 18 of the United States Code and 
that such willful false statements may jeopardize the validity of a 
Patent Application or any patent issuing thereon. 



f^cW^> ^ Aff ^_ DATE: 3* M Ar tW VtfS 

RICHARD L. GREENE 



YO987-074 



Of i 



'1- 



Zurich Research Laboratory 
8803 RuschJikon, Switzerland 

c J I 4 J J ljd. } °^ ele t h ^ n ^1>724 81 11 

TeleprinterTlTPS CODE 2RL 



ACTIVITY REPORT 
MAY-JUNE, 1986 



A^ust 15, 1986 



tun 



REC 'D-SEP 03 19S5 



MATERIAL SCIENCE T. Schneider, Mgr. 



SURFACE & MATERIAL SCIENCES E. Courtens, Mgr., Project 4181 



Novel Research 



Possible Iligh-T c Superconductivity in the Ba-La-Cu-O System 
J.G. Bednorz and K.A. Muller (Project 4196) 

We observed a steep decrease of resistivity in sintered Ba-La-Cu-oxide samples, with the highest 
temperature of the onset in the 35 K range (Fig. 1). 

The Ba-La-Cu-O system exhibits a number of oxygen deficient phases with perovskite-like 
layer-type structures. These are characterized by mixed-valent copper ions (Cu 2+ and Cu 3 + ) and 
itinerant electronic states. In addition one expects polaron formation induced by the strong 
Jahn-Teller effect of Cu 2+ in an octahedral oxygen environment. Thus our Ba-La-Cu-0 system 
was anticipated to have considerable electron-phonon coupling and metallic conductivity. 

Compounds with the composition Ba(x)La(5-x)Cu(5)0(5[3-y]) have been prepared in 
polycrystalline form. Samples with x < 0.2 and y > 0, annealed below 900°C under reducing 
conditions, consist of three phases, one of them a perovskite-like mixed-valent copper compound 
with K 2 NiF 4 type structure. Upon cooling, the samples show a linear decrease in resistivity, then 
an approximately logarithmic increase, interpreted as a beginning of localization. Finally a steep 
decrease by up to three orders of magnitude occurs, reminiscent of the onset of percolative 
superconductivity. The highest onset temperature is observed in the 35 K range It is markedly 
reduced by high current densities (Fig. 1). The slow sensitivity decay towards low temperatures 
might possibly result from 2D superconducting fluctuations of perovskite layers of one of the 
phases present. 



IBM CONFIDENTIAL 



ACTIVITY REPORT 



PHYSICS 



MAY-JUNE 1986 



-2- 



0.010 



0.008 



0.006 



£ 



0.004 



0.002 



1 • 4 



o 7.5 A/cm 2 
« 2.5 A/cm 2 
* 0.5 A /cm 2 



10 20 



30 40 
T (K) 



50 60 




0.4 0.2 0 0.2 0.4 06 .0.8 
WAVE VECTOR (A" 1 ) 



FIG. 1 



I 



[060 



= % /a SI CM 



FIG 2 



IBM CONFIDENTIAL 



Date: 6 October 1986, 15:37:18 EDT From: RGREENE at YKTVMZ To: KAM at 
ZURLVM1 

Alex; 

Have you made any decision on my proposed specific heat experiment? 
I am anxious to try it. I think I can do it rather quickly after getting 
some samples. It may be difficult to see the transition near 30K because 
of a large phonon background but at the very least we could get a good 
estimate of the electron density of states and the Debye phonon contrib- 
ution. Once I have a good specific heat between 2K and 40K I can make a 
better effort to resolve the electronic effect at Tc if it is small... I 
think I can see a 1% effect if the transition is not too smeared in tem- 
perature. Perhaps you would like to come to Yorktown and work with me 
on this experiment? Let me know. Best regards. 

Rick 

P.S. This is a good time for me to do some experiments on your exciting 
new compound since I am not heavily involved in other projects yet. 
I could get access to tunneling and neutron scattering equipment 
which would be very useful for seeing which phonons (if any) are 
involved in causing such a high Tc. 



Date: 14 October 1986, 10:42:19 EDT From: RGREENE at YKTVMZ To- 
at ZURLVM1 



KAM 



Hi Alex: 

This note is to give you my user id and node on the VM system. 
You can see them above. When you send the samples for the specific heat 
experiment let me know via VM. My office at Yorktowm is 02-026. I will 
make the specific heat my highest priority and should be able to start 
the experiment as soon as the samples arrive. I will keep you informed 

on the progress of the experiment it will probably take a few weeks 

to get reliable data assuming there are no unexpected problems. 

As I said on the telephone you can ignore the sample dimensions 
sent to you by my manager C. Tsuei. He did not talk to me before sending 
you his VM note and he did not understand the requirements of the specific 
heat apparatus. What I need are samples to cover an area of 2mm x 2mm on 
the bolometer. Some extra samples will also be necessary in case we break 
or lose the primary samples. It would be best to not compress the samples 
or bind them together with any foreign materials which could alter the 



specific heat. 



Best Regards, 

Rick 



Date: 15 October 1986, 15:02:34 EDT From: RGREENE at YKTVMZ To: SANDRO 
Sandro; I have a court at 5pm. Do you want to play? 



Rick 



Date: 16 October 1986, 09:06:42 EDT From: RGREENE at YKTVMZ To: 



GGRIN 



1 




I'm thinking about taking my son to Mohansic tomorrow afternoon around 
1:30. If you want to join us let me know. 

Rick 



Date: 16 October 1986, 13:27:32 EDT From: RGREENE at YKTVMZ To: JBMART 

The reference is PRL 57, 1177(1986). I think a pressure experiment might 
be interesting. Let me call Chaikin and Brian first then I'll get back 
to you. 

Rick 



Greene 



Date: 20 October 1986, 08:51:36 EDT From: RGREENE at YKTVMZ To: 
LOUGHRAN at ALMVMC 

Hi Diane; 

Starting to get cold around here but at least the sun is shining. 
Hope all is well with you. You can discard the Chaikin-Greene manuscript. 
It's been published and I have the reprints .Thanks for forwarding any 
remaining mail that comes to Almaden it takes a long time for scien- 
tific types to know when one has moved. I'll be seeing you in Jan. 

Regards, 

Rick 



Date: 20 October 1986, 15:18:13 EDT From: RGREENE at YKTVMZ To: KAM 
at ZURLVM1 

Alex; 

The samples have arrived. They are bigger than I expected and all 
appear to be compressed pellets. Before I start on the specific heat I 
need to know a few things. 

1. What is the difference between the samples marked I (red) and II (black)? 

2. Have the samples been compressed with any foreign material, such as a 
binder? 

3. Can the samples be cut without falling apart? If so do you recommend 
using a string saw or a razor blade or something else? Will water damage 

them? 



2 



4. Has the magnetic susceptibility been measured on any of these samples 
or on other samples from the same batch? I may want to measure the 
resistivity or susceptibility on these particular samples to make sure 
they exhibit the behavior you found before spending a big effort on the 

specific heat. 



We are measuring the background specific heat of our apparatus up to 40K 
tomorrow. . .hopefully by the end of the week we will begin your samples 
so please call or send me via VM the answers to the above questions as 
soon as possible. 

Best regards , 

Rick 



Rick 



Date: 23 October , 1986, 13:43:17 EDT From: RGREENE at YKTVMZ To: BED 
at ZURLVM1 cc: KAM at ZURLVM1 

Hi George , Alex; 

Just a note to keep you informed of our progress . We are almost 
finished with the background specific heat. Tomorrow we will mount a 25mg 
(slice of your sample BLC02..-.it should take about a week to get the data 
in the earth's magnetic field. It probably will be necessary to also 
measure the specific heat in a magnetic field to accurately determine the 
superconducting contribution. Do you have any data on the critical field 
for this sample. ..if not we can measure it ourselves. Also I need to know 
if the samples you sent roe are each a single phase. .... from your x-ray 
studies. I haven't received your preprint yet ... .perhaps some of my 
questions are answered there. 

I will be away from the lab tomorrow and look forward to your 
response on Monday. Best regards. 

Rick 



Date: 23 October 1986, 14:00:11 EDT From: RGREENE at YKTVMZ To: MALOZEM 
Alex; 

Sorry I haven't gotten back to you but I have been very busy with 
two exciting experiments the specific heat of the new Zurich high 



temperature superconductor and the 2D melting X-ray experiment with Paul 
which finally looks like it will work. I'm not really sure if there are 
any easily defined X-ray experiments that can be done to prove or disprove 
the nice model you presented this morning but I will think more about 
this. However given my present experimental committments it will be a 
few months before I could realistically do anything. Keep me informed. 
Thanks . 



Rick 



Date: 23 October 1986, 14:27:22 EDT From: RGREENE at YKTVMZ To- BED 
at ZURLVM1 

George; Thanks for the Susceptibility info. I'm glad that I chose BLC02 
I for the first experiment . How wide in temperature is the para-diamagnetic 
transition in this sample? Regards. 

Ri <* 

PS 8 ' " .nx>° Ct0ber 1986 ' " = 58735 SET From: j.g.bednorz 
BED at ZURLVM1 To: RGREENE at YKTVMZ 



Hi Rick 

Here are the results of our susceptibility measurements, done 
on the samples You got from me. I'll give You the temperatures 
where the para- to diamagnetic transition occurs. 



BLC02 I 32K 
BLC08 I 13-14K 
BLC021I 25K 



BLC02 II 26-27K 
BLC08 II 25-26K 
BLC021II 27-28K 



So You don't need to involve somebody else with these measurements, 
which I prefere doing myself here. 

While typing this, I got the message that You send a note. 



Salu 
George. 



Date: 23 October 1986, 16:00:52 EDT From: RGREENE at YKTVMZ To: TFHEINZ 
Tony; 

I can't serve on the colloquim committee this year. I'll try to think 
of possible speakers however. Sorry and thanks for thinking of me. 

Rick 



Date: 23 October 1986, 17:32:09 EDT From: RGREENE at YKTVMZ To* GRANT 
at ALMVMC ' 

Hi Grant; 

Where have you been hiding? I need to talk to you since you 
didn t answer my last note. I'll be here on Monday.. try me then. 



A 




at Yorktown. Thanks and regarus. 

Rick 



Date: 27 October 1986, 08:32:34 EST From: RGREENE at YKTVMZ To: GGRIN 

Got your note too late sorry I missed the big game. Let f s try the 

real, poI f oflme . for a 



Date: 28 October 1986, 17:30:52 EST From: RGREENE at YKTVMZ To: BED 
at ZURLVM1, KAM at ZURLVM1 

Hi George, Alex: 

Did you get the last two notes that I sent you? I'm 
measuring BLC02 this week. nothing definitive yet. I'll keep you in- 
formed. What is the critical field of this sample? Is BLC02-I all the same 
phase? I haven't received your preprint yet... have you sent it? Best 
regards . 

Rick 



Date: 29 October 1986, 17:20:53 EST From: RGREENE at YKTVMZ To: GGRIN 
Hey Rod; 



5 



Date: 29 October 1986 16-41*?? cr T v , ■ 

BED at ZURLVM1 To: RGREENE at YKWMZ ^ J ^- bednorz 

Hi Rick, 

11*11 5°u l6ttin « y° u wait so lo "8 to get an answer. Alex told 
me that he sent the reprint already 10 days ago. I have sent 
you a second one today, in case the letter got lost somewhere. 

Concerning your questions: 

From our measurements we can tell you that the critical field 
Hc2 is higher than 1.5 kG. 

Now about the phases present in our samples: 

Jrfno It o phases: ° cub - Perovskite/tetrag. P erovskite/CuO 
bLAsVz II 2 phases: " / « j 



phases: " / 

BLC08 I 2 phases: " / 

BLC08 II 1 phase : / 

BLC021I 2 phases: 

BLC021II 1 phase : / 

Best regards also from Alex 

George. 



/ — 
/ — 
/ — 
/ — 



arALMv^C° Ct ° ber ' 09:20:04 EST From: RGREENE * fc YKTVTfZ To: GRANT 

Hi Grant ie; 

mo™ Vm here i ;- where are y°"1 Don't even have a phone answer any 

more. How come you didn't answer the questions in my last note. 

tLill th H 3M iT* 108 1 su P°ssed to share a room with Torrance starting 
Sunday nite I . not sure if he's still coming or how long he's staying 
Check with him and you can share the room with us or replLe him. Let me 

Greene 



Date: 30 October 1986, 09:31:20 EST From: RGREENE at YKTVMZ To- BED 
at ZURLVM1, KAM at ZURLVM1 ° 

Hi Alex and George: 

. 1 j ust tried to reach you by telephone without success 

9 * n ° te ' We hSVe measured the specific heat(C) of BLC02-I from 

Ik u anal y sis is not Vet complete but the prliminarv data does not 

show any bump in C near or below 32K. However at this stage we could only 
see a bump or jump if it was greater than 10% of C so more accurate ex- 



6 



penraents will be required. Since BLC02-I is a 3 phase sample it was not 
a good choice for the measurement since I will not be able to analyze the 
data for density of states and Debye Temp. Do you know how much of each 
phase is present in this sample? Also is the cubic perovskite a metal or 
insulator? 

It would be better if you had some single phase single crystals 
of the tetragonal phase. Is this possible? We could measure samples as 
small as a few milligrams. 

Without crystals I am planning to measure BLC08-II next since this 
is a single phase. Once you send me the info on the chemical composition 
and structure of this phase I can analyze the data and hopefully get re- 
sults that we can publish. The measurements will take another week if all 
goes well. If we have to put on a magnetic field this will take several 
more weeks... specific heat data is tedious to obtain and analyze even 
with a computer. 

Please answer the above questions as soon as possible. I am still 
waiting for your preprint ... the first one must have gotten lost. Did you 
send it by external mail? Best regards. 

Rick 



Date: 30 October 1986, 18:30:43 SET From: i.gbednorz 
BED at ZURLVM1 To: RGREENE at YKTVMZ J-g-oednorz 



Hi Rick, 

BLC021II or BLC08II would be good to try. 
the BLC02111 shows a more Pronounced resistivity drop, as compared to 
sample I. BLC08II I could not check till now. 

The composition is Ba0.15 Lal.85Cu04-x and BaO . lOLal . 90CuO4-x 

respec- 

tively.The structure of La2Cu04 is a layered perovskite of K2NiF4 

type . 

^ The pure material is orthorhombically distorted. Exchanging La by 
cell ^ le3dln8, 3S We belief . to the formation of a tetragonal unit 

Our powder diffraction pattern can be indexed with a bodycentered 
lattice and a=3.79A and c=13.21A for xBa around 0.1. For crystals 
crystal °'° 2 1 ^ Checked the la «i" parameters by single 

precession experiments. But here we aready have the problem. These 
crystals have been obtained from powders with xBa=0.1, so we have 
to expect seggregation and it will take a while, to get the crystals 
with a composition where the resistivity drop is observed in the 

powders . 

To your question about the cubic perovskite.it shows metallic 

conduc- 
tivity as well. 

I really hope, that you get the preprint very soon. 



7 



Best regards George. 



at t ZURLWll 0Ct ° ber ' 15:06:11 EST From: RGREENE " YKTVMZ To: BED 

George; Thanks for your quick answer to my questions. I forgot to ask you 
iJrn? U T ™ relative wei « ht - of the 3 phases in sample 

f ll' J S ° 1 may Sti11 be able co Set some useful information 
rrom the data we have taken so far. 

I also just realized that you could send me the preprint via VM 
assuming it was typed on line. Please see if your secretary 
can do this. Thanks and regards. 

Rick 



!!f tTMfJ 0 ^" 1986 ' 16:58:28 EST From: RGREENE at YKTVMZ To: JERRYT 



at ALMVMC 
Hi Jerry; 



16th TV - u° r °V r °° m at the Hyatt sta ^ting Sunday nite the 

16th I m not sure when I 11 arrive but they have your name attached to 
the room also and at s guaranteed for late arrival. See you there. I saw 

lltl^l n re ? ntly about 311 o^ic f erromagnet .... I think in JETP 
letters. Do you know about that work? 

Rick 



Date: 4 November 1986, 17:00:53 EST From: RGREENE at YKTVMZ To: SANDRO 

LrroTl Si? to ^ rrow -:- so "y-Next week. If I can change my schedule to- 
morrow I will call you in the morning. 



Rick 



af ZURL4l N ° Vember 1986 ' 10:04:02 EST Fr ° m: RGREENE at YKTVMZ To: BED 
Hi George; 

nhnnfl M J*° 1 h f v ? not « iven -in fact I just tried to reach you by 

phone. My terminal zs not working since I just changed my office so It may 
take me a little longer to respond to messages. 

At any rate I have finished the specific heat measurement from 4-35K 
in zero magnetic field. It will take a few days to finish the data anal- 
ysis but there is no obvious bump in the specific heat indicating 
superconductivity. This is not really too surprising given the very broad 
transition you have found in resistivity and susceptibility. 

I expect to get some useful information from the data anyway but 

I'kti «p L " eed the eX3Ct com P° sit ion of BLC021-II.Is it 
Ba 15Lal.85CuO(4-.15)? Please send this as soon as possible by VNET I 
will get back to you and ALex later with more info. Regards. 



8 



Rick 



Date: 12 November 1986, 09:19:56 EST From: RGREENE at YKTVMZ To: GRANT 
at ALMVMC 



Greene 



Date: 13 November 1986, 13:54:49 EST From: RGREENE at YKTVMZ To: 
MALOZEM 

Alex; 

I'll be happy to talk about the prospects of using magnetic X-ray 
scattering for thin films and interfaces. It will only be a summary of 
what has been done and my thoughts on what else could be done. The rest 
of your proposed program looks great. It's a good idea to have such an 
internal meeting. 

Rick 



Date: 14 November 1986, 10:17:09 EST From: RGREENE at YKTVMZ To: BED 
at ZURLVM1, KAM at ZURLVM1 

Hi Alex and George; 

I will be away from the lab until 24 Nov. so I thought I would 
let you know the present status of the specific heat (SH) experiment and 
my future plans. 

So far we have measured BLC021 from 3-35K. There is no evidence 

for a bump in SH anywhere to a 5% accuracy. I have analyzed in detail 

the data between 3-10K. Here the SH is linear on a C/T vs T2 plot. The 
intercept gives a value for gamma of 5.9 mj/mole-K2. This is a rather 
large value compared to other metals and suggests that most of the BLC021 
sample is in the normal state. However to be sure of this we roust measure 
the sample in a magnetic field large enough to suppress the 
superconductivity. This we will start while I am away. Also we must run 
a test sample such as copper or silicon to know the accuracy of our gamma 
determination. All this will take 2-3 more weeks. As you see it takes 
considerable effort to do a reliable specific heat measurement which makes 
it very important that we have well characterized, single phase samples. 
As we discussed yesterday George it may be better to do the SH experiment 
on a bunch of single crystals if you can prepare them. Five mg of material 
should be enough to get reliable data. 



9 



We will also measure the critical £ield up to 9T via resistivity 
I want to do this first so I have some idea of the field necessary to get 
the normal state at 3K. . . .our SH apparatus has a field of 5T maximum. 

I'll talk with you when I return. I am still quite excited about 
these new materials and hope that we can continue to collaborate on var- 
ious experiments even if the specific heat does not give evidence for bulk 
superconductivity. I should remind you that it took many years of work 
before the BaPbBi Oxides were shown to be bulk Superconductors. 

Best regards, 

Rick 



at t ALMWlC N ° Vember 1986 ' 09:43:48 EST From: RGRE£ NE at YKTVMZ To: PARKIN 



Hi Stuart; 

Thanks for your note. I haven't heard from Helmut but he is 
probably very busy starting his new job. Haven't heard about the Japan 

proceedings either are you still interested in organic metals? What 

is happening with your work on thin films? I expect to be out to San Jose 
sometime in January and you can bring me up to date: 

Until then I am very busy with X-ray scattering and some other ex- 
periments on new inorganic materials. Have a good holiday season. 

Best regards 



Rick 



Date: 25 November 1986, 10:35:50 EST From: RGREENE at YKTVMZ To- 
at ZURLVM1, KAM at ZURLVM1 



BED y 



Hi Alex and George; 

I have returned from my trip and will once again start work 
on Your new superconductor. This week is the Thanksgiving holiday so not 
much will happen until next week. The specific heat apparatus is now 
modified to make measurements in a magnetic field. . . .however we must first 
calibrate and check that it works with some known material. 

Please tell me what is happening with your studies of time de- 
pendent effects . Is the sample BLC021 still good. .. .we have not yet 
measured the resistivity in a field as a function of T but we plan to along 
with the specifi c heat experiment. Perhaps you should send me some new 

single crystals for the next experiment I don't want to waste time 

on a bad sample. 

I would like to send an abstract to the March APS meeting on the 
specific heat results. Is this agreeable with you? The abstracts are due 
the end of next week (Dec. 5) so let me know soon. At this stage there is 
not much definitive to say but I can still write a general abstract about 
specific heat and I m sure I will have definitive results by the time of 
the meeting. 



10 



Best Regards, 

Rick 



Date: 26 November 1986, 09:56:43 EST From: RGREENE at YKTVMZ To: KAM 
at ZURLVM1 

Hi Alex; 

Are you sending your susceptibility preprint to people outside 
of IBM? If so Ted Geballe at Stanford would like a copy. . .he saw your 
paper in Z. Physic and called me to see if I knew about your work. 

I can send him a copy if you are agreeable. Please let me know 
about this and more importantly the answer to my note of yesterday. 

— — Best reg ards » 



Date: 1 December 1986, 17:31:01 EST From: RGREENE at YKTVMZ To: KAM 
at- ZURLVM1, BED at ZURLVM1 

Hi Alex and George: 

Here is a draft of the abstract that I would propose submitting 
to the APS March meeting. Please make any changes or comments and let me 
know today- I lopk at this as a way to publisize your work in the USA and 
to present whatever specific heat results are obtained by March. 



POSSIBLE HIGH Tc SUPERCONDUCTIVITY IN THE Ba-La-Cu-0 SYSTEM 



We report measurements on new oxide superconductors of the composition 
La(2-x)Ba(x)CuO(4-y) with x«l and y>0. Polycrystalline samples with 
x=,15 show a resistivity drop of three orders of magnitude and a transi- 
tion from Pauli paramagnetism to diaraagnet ism with an onset temperature 
between 30-35K. (ref 1 and 2.... your two papers). The transition is 
complete by 10K and magnetic field studies suggest superconductivity of 
a percolative or granular nature. Our specific heat experiments indicate 
a large electron density of states but no evidence of a sharp jump near 

Tc consistent with the small Meissner signal observed (2% of complete 

flux expulsion) and the broad transition width. These measurements, along 
with X-ray and critical field results, will be analyzed for the possi- 
bility of high Tc superconductivity in these new oxide materials. 



11 



The authors would be the three of us and Steve VonNolnar (whose apparatus 

I am using) possibly I would add Al Torresen (Steve's assistant) 

without whom the specific heat experiments could not have been done. 

The abstract could perhaps be a bit longer but there may not be much space 
after the authors and references are included. 



Regards , 

Rick 



Date: 2 December 1986, 09:17:12 EST From: RGREENE at YKTVMZ To: RAM 
at ZURLVM1 

Alex; 

I scheduled your seminar for 8 Jan at 3 : 30pm. . . . this was the only 
time I could get a room. Please send me a title and short abstract so I 
can get it on the lab calender as soon as possible. Do you need a hotel 
reservation? Regards. 

Rick 



P.S. Plan on saving some time on 9 Jan. to discuss our specific heat 
data. If you would like to go out together for dinner on the 8th 
let me know. 

Date: 4 December 1986, 10:48:02 EST From: RGREENE at YKTVMZ To: BED 
at ZURLVM1 

Hi George; , 

I just tried to telephone you. I am measuring the resistance 
and critical field of sample BLCO-21. So far it reproduces the data in 
your Z. Physik paper... I don't see a bump except perhaps near 25K (but I 
need to take more points). The surprising thing is that a small field 
(1000 Oe) increases the Resistance to the value at 25K but at higher 
fields (up to 7Tesla) there is almost no more change in R. Tell you more 

when I have more data so far it suggests that doing the specif ic heat 

in low field will be useful. 



Would you please send me whatever info you have on the structure 
of the superconducting phase i.e. a picture and a powder X-ray that gives 
the Bragg peak positions. 

What have you learned about the time changes in these samples? I 
would like some fresh single phase samples for our next specific heat 
experiment. ..to begin at the end of next week. If you have single crystals 
,_th,at_JKOul d even be batt er hnt T realizp. th is is a Hiffim U 



negaras , 



12 



Rick 



Date: 5 December 1986, 10:56:34 EST From: RGREENE at YKTVMZ To: ORR 
OK. What are you up to? Dropin and see me sometime in vonMolnars lab. 

Rick ______ 



Date: 5 December 1986, 11:10:42 EST From: RGREENE at YKTVMZ To: KAM 
at ZURLVM1, BED at ZURLVM1 

Hi Alex and George: 

I'm getting some good critical field results now although I still 
don't totally trust my contacts . The resistance vs. temp, follows your 
data but there seems to be two superconducting regions (perhaps 2 
phases)., one below 22K and the other below 33K. The critical fields are 
very different in these two temperature ranges. The good news is that I 
am getting a critical field vs temp curve between 20-30K and this will 
alllow roe to estimate gamma to compare with the specific heat gamma. 
Incident ly the critical field at 4K is greater than 7Tesla (as expected <T 
for a high Tc material) so we may eventually want to go to the MIT magnet 
lab to^measure it better. 

The specific heat exp. is progressing nicely and we will be finished 
with all our calibrations next week. What sample do you recommend that I 
use based on your recent work? 

As soon as I have collected and plotted all the critical field data 
I will send you a figure along with the abstract to the March meeting. 

Best regards, 

Rick 



P.S. Please send me whatever info you have on the structure of the SC 
phases . 

I am giving an internal journal club seminar on your resistivity and 
susceptibility papers . 



Date: 8 December 1986, 09:26:48 EST From: RGREENE at YKTVMZ To: 
LOUGHRAN at ALMVMC 



13 



Rick 



Date: 3 December 1986, 16:39:02 SET From: KAM at ZURLVM1 To: RGREENE 

at YKTVMZ 

Rick, here is the title and abstract for my seminar : 

'Superconducting and Structural Properties of the BaLaCuO System 1 

Resistivity and susceptibility measurements as well as x-ray powder 
analysis carried out at the Rueschlikon laboratory will be described. The 
electric and magnetic data indicate the existence of a percolative 
superconductor with onset above 30 K.The newest magnetisation measure- 
ments as a function of temperature and field proove the presence of a 
superconductive glass. The highest Tc sampels correlate with an 
orthorhorabic- tetragonal structural phase transition. 

please check for the english, thanks 

Alex 



Date: 9 December 1986, 10:29:48 EST From: RGREENE at YKTVMZ To: GGRIN 

Let's stick to our Weds tennis 4; 30 right? 

Rick 



Date: 9 December 1986, 10:31:06 EST From: RGREENE at YKTVMZ To: POME RAN 
Mel; 

I can't take the court on Thurs. so why don't we just put off our game 

until next week. 



14 



Rick 

Date: 9 December 1986, 10:37:27 EST From: RGREENE at YKTVMZ To: BED~ 
at ZURLVM1, KAM at ZURLVM1 

Hi George , Alex; 

Thanks for your note George. I will send you the Critical field 
data today. It seems to reproduce your low field results and has the data 
up to 7Tesla....I could go to 9T but will do that later. I assume from 
your note that you think that BLC021 is still a single phase.. .is that 
correct? I will use this sample for the specific heat in a magnetic 
field. 

I am a little puzzled by the critical field data... it suggests that your 
susceptibility data was measuring the superconductivity that occurs below 
20K and the superconductivity above 20K may not be a bulk effect. It's 
also a litte disturbing that I measured such a large linear term in the 

specific heat in earth field the measurements at 5T should clarify 

this however - 

Can you tell me the density of the SC phase? I need this to es- 
timate gamma from the critical field slope. Also what is your estimate 
of the value of the resistivity just above Tc? I assume a single crystal 
would be at least 10 times lower. Also I would like to know your estimate 

of the Pauli susceptibility above Tc from your data this will give 

another estimate of gamma. 

Thanks for sending me your info and figures of the structure.. I 
hope it arrives before next Tuesday. 

Best regards, 
Rick 



ubzb: y December 1986, 11:32:57 EST From: RGREENE at YKTVMZ To: MALOZEM 

I don't know Creuzet that well but he seems to have done some good work 
and seems to know what he's talking about. I'm not sure how independent, 
creative or hardworking he is. What would he be doing here? How closely 
working with an RSM? Who with? 



15 




Rick 



Date: 9 December 1986, 14:34:51 EST From: RGREENE at YKTVMZ To: POMERAN 
Mel; 

OK for Monday. SEe you there unless you hear otherwise. 

Rick 



Date: 8 December 1986, 18:56:40 SET From: j.g.bednorz 
BED at ZURLVM1 To: RGREENE at YKTVMZ 

Hi Rick Sorry that you had to wait for the answer since Thursday. I ' ve been 
in Germany since Friday. In November I told you on the phone, that 
something happened to that sample BLC021II which I measured again one 
month after the first resistivity run. The resistivity curve showed a 
peak at 34K and a shoulder occurring around 25K after a 60 percent drop. 
At that time I was also surprised about the magnetic field dependence in 
the low temperature part. The resistance was increased by fields between 
0-0.4 Tesla but seemed to saturate at values above, whereas the field 
dependence of the peak at 34K was smaller. It would be good to compare 
our results, especially as you have the possibility to go to higher fields 
than 0.7 Tesla, which is the limit for our resistivi- ty system. Unfor- 
tunately I do not see the occurrence of a new phase related to the 
appearence of that shoulder in the resistivity. 

Concerning your internal seminar, I will send you an X-ray powder spectrum 
and the structure of La2Cu04, which I've drawn already, using the infor- 
mation given in a German article. You can even have the viewgraphs. We 
should discuss questins about the structure at the phone. 

Best regards 
George . 



Date: 9 December 1986, 18:47:08 SET From: j.g.bednorz 
BED at ZURLVM1 To: RGREENE at YKTVMZ 

Hi Rick, 

Thank you for your quick answer. I just discussed with our Japanese guest 
Masaaki Takashige, who is involved in the susceptibility measurements. 
First of all you should not be worried about about the susceptibility data 
shown in the preprint, because the samples shown there are not single 
phases. You will see from the X-ray pattern that the amount of the for- 
eign phase can be very large , greater than in BLC021 I. Single phase means, 
that in the X-ray diagrams we only can detect the La2Cu04:Ba. The small 
suscepti- bility could indicate that only parts of that phase is super- 
conducting, for instance an intragranular network. That is the reason, 
why we think the density of La2Cu04 (from the X-ray data = 7 g/ccm) would 
not lead to a correct estimation in your case. The Pauli susceptibility 



16 



of sample BLC021II, this sample is not shown in the paper, shows a field 
dependence close to Tc, this dependence is getting weaker with increasing 
temperature, and we expect it to vanish 10 or 20 de- grees higher, but in 
case of this sample it has not been confirmed, I'll give you values at 
32-33K for the mass susceptibility: 

0,3 Kgauss 1.28 E-7 ccm/g 

5-0 1.35 E-6 ccm/g 

. 10 *° ' 161 E_6 ccm/g Especially for the low field value 

we have to be aware of a large error. 

For the resistivity value: My measurement (second one, where I realized 
the magnetic field dependence) showed a peak value of 7.36 E-3 Ohm era. 

Concerning the results of the Japanese group: Do you know more about it? 
How did they measure the 40% Meissner effect, did they measure ac or dc? 
Is something known about the magnetic field they applied? I think they 
believe the metallic perovkite phase is responsible for the 
superconductivity, whereas we found that the single phase samples eon- 
tain fiaSCttOif** in the powder dlf***etien pattern: show the highest 
susceptibilifcia* , ¥ou will get *he aepies ef fch* results mb moon us they 
are plotted. 

Best regards 

George. can be very large, larger than 
in BLC021. Talking about single phase samples 

les , 



Date: 10 December 1986, 10:48:47 EST From: RGREENE at YKTVMZ To: GRANT 
at ALMVMC 

I haven't forgotten you.... just busy as hell with this 30K superconductor 
and can ! t think about anything else. Happy Holidays Turkey. 

Looks like I won't have time to ski... too much physics to do. 

l e Greene 



17 



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