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48
Sep 18, 2013
09/13
by
J. -C. Griveau; K. Gofryk; D. Bouëxière; E. Colineau; J. Rebizant
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We report on the crystal structure, magnetic susceptibility, specific heat, electrical and thermoelectrical properties of AmPd5Al2, the americium counterpart of the unconventional superconductor NpPd5Al2. AmPd5Al2 crystallizes in the ZrNi2Al5-type of structure with lattice parameters: a = 4.1298 A and c = 14.7925 A. Magnetic measurements of AmPd5Al2 indicate a paramagnetic behavior with no hint of magnetic ordering nor superconductivity down to 2 K. This aspect is directly related to its 5f6...
Source: http://arxiv.org/abs/1201.5664v1
4
4.0
Jun 29, 2018
06/18
by
K. Gofryk; J-C. Griveau; P. S. Riseborough; T. Durakiewicz
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We present measurements of the thermoelectric power of the plutonium-based unconventional superconductor PuCoGa$_{5}$. The data is interpreted within a phenomenological model for the quasiparticle density of states of intermediate valence systems and the results are compared with results obtained from photoemission spectroscopy. The results are consistent with intermediate valence nature of 5$f$-electrons, furthermore, we propose that measurements of the Seebeck coefficient can be used as a...
Topics: Condensed Matter, Strongly Correlated Electrons
Source: http://arxiv.org/abs/1610.07581
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160
Sep 21, 2013
09/13
by
K. Gofryk; D. Kaczorowski; T. Plackowski; A. Leithe-Jasper; Yu. Grin
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RPdBi (R = Er, Ho, Gd, Dy, Y, Nd) compounds were studied by means of x-ray diffraction, magnetic susceptibility, electrical resistivity, magnetoresistivity, thermoelectric power and Hall effect measurements, performed in the temperature range 1.5-300 K and in magnetic fields up to 12 T. These ternaries, except diamagnetic YPdBi, exhibit localized magnetism of $R^{3+}$ ions, and order antiferromagnetically at low temperatures ($T_{N}$ = 2-13 K). The transport measurements revealed behavior...
Source: http://arxiv.org/abs/1106.3763v1
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76
Sep 23, 2013
09/13
by
Xin Lu; F. Ronning; P. H. Tobash; K. Gofryk; E. D. Bauer; J. D. Thompson
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We report soft point-contact spectroscopy studies of URu2Si2 both in the hidder order (HO) and the large-moment antiferromagnetic (LMAF) states accessed by pressure. In the HO state at ambient pressure, the spectroscopy shows two asymmetric peaks around the Fermi energy that emerge below the hidden order temperature T_{HO}. In the LMAF state at higher pressures, the spectra are remarkably similar to those in the HO state, indicating a similar Fermi surface gapping in the HO and LMAF states and...
Source: http://arxiv.org/abs/1112.5669v1
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55
Jul 20, 2013
07/13
by
Dong-Jin Jang; J. B. Hong; Y. S. Kwon; T. Park; K. Gofryk; F. Ronning; J. D. Thompson; Yunkyu Bang
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We report specific heat capacity measurements on a LiFeAs single crystal at temperatures down to 400 mK and magnetic fields up to 9 Tesla. A small specific heat jump at Tc and finite residual density of states at T=0 K in the superconducting (SC) state indicate that there are strong unitary scatterers that lead to states within the SC gap. A sub-linear magnetic field dependence of the Sommerfeld coefficient \gamma(H) at T=0 K is equally well fitted by both a nodal d-wave gap as well as a sign...
Source: http://arxiv.org/abs/1203.1362v1
3
3.0
Jun 30, 2018
06/18
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K. Gofryk; B. Saparov; T. Durakiewicz; A. Chikina; S. Danzenbächer; D. V. Vyalikh; M. J. Graf; A. S. Sefat
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Fermi-surface topology governs the relationship between magnetism and superconductivity in iron-based materials. Using low-temperature transport, angle-resolved photoemission, and x-ray diffraction we show unambiguous evidence of large Fermi surface reconstruction in CaFe$_{2}$As$_{2}$ at magnetic spin-density-wave and nonmagnetic collapsed-tetragonal ($cT$) transitions. For the $cT$ transition, the change in the Fermi surface topology has a different character with no contribution from the...
Topics: Strongly Correlated Electrons, Condensed Matter
Source: http://arxiv.org/abs/1404.1095
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50
Sep 22, 2013
09/13
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K. Gofryk; A. S. Sefat; M. A. McGuire; B. C. Sales; D. Mandrus; J. D. Thompson; E. D. Bauer; F. Ronning
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We report a doping, magnetic field and low-temperature dependent study of the specific heat of the iron-arsenide Ba(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$ at under (x=0.045), optimal (x=0.08) and overdoped (x=0.103 and 0.105) regimes. By subtracting the lattice specific heat the temperature and magnetic field dependence of the electronic specific heat has been studied. The temperature and field dependencies of the superconducting part of $C_{p}$ exhibit similar behavior for all doping...
Source: http://arxiv.org/abs/1004.4576v3
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107
Sep 19, 2013
09/13
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K. Gofryk; A. B. Vorontsov; I. Vekhter; A. S. Sefat; T. Imai; E. D. Bauer; J. D. Thompson; F. Ronning
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We report on the effect of annealing on the temperature and field dependencies of the low temperature specific heat of the electron-doped Ba(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$ for under-(x = 0.045), optimal- (x = 0.08) and over-doped (x = 0.105 and 0.14) regimes. We observed that annealing significantly improves some superconducting characteristics in Ba(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$. It considerably increases $T_{c}$, decreases $\gamma_{0}$ in the superconducting state and suppresses the...
Source: http://arxiv.org/abs/1009.1091v2
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39
Sep 22, 2013
09/13
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K. Gofryk; A. S. Sefat; E. D. Bauer; M. A. McGuire; B. C. Sales; D. Mandrus; J. D. Thompson; F. Ronning
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We report the field and temperature dependence of the low-temperature specific heat down to 400 mK and in magnetic fields up to 9 T of the electron-doped Ba(Fe0.92Co0.08)2As2 superconductor. Using the phonon specific heat obtained from pure BaFe2As2 we find the normal state Sommerfeld coefficient to be 18 mJ/mol.K^2 and a condensation energy of 1.27 J/mol. The temperature dependence of the electronic specific heat clearly indicate the presence of the low-energy excitations in the system. The...
Source: http://arxiv.org/abs/1001.4564v1
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44
Sep 23, 2013
09/13
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C. Stock; D. A. Sokolov; P. Bourges; P. H. Tobash; K. Gofryk; F. Ronning; E. D. Bauer; K. C. Rule; A. D. Huxley
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We report neutron scattering measurements of critical magnetic excitations in the weakly ferromagnetic superconductor UCoGe. The strong non-Landau damping of the excitations we observe, although unusual has been found in another related ferromagnet, UGe2 at zero pressure. However, we also find there is a significant anisotropy of the magnetic correlation length in UCoGe that contrasts with an almost isotropic length for UGe2. The values of the magnetic correlation length and damping are found...
Source: http://arxiv.org/abs/1109.4541v1
3
3.0
Jun 30, 2018
06/18
by
B. G. Ueland; C. F. Miclea; K. Gofryk; Y. Qiu; F. Ronning; R. Movshovich; E. D. Bauer; J. S. Gardner; J. D. Thompson
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We present experimental results for the heavy-electron compound CeCu$_{4}$Ga which show that it possesses short-range magnetic correlations down to a temperature of $T = 0.1$ K. Our neutron scattering data show no evidence of long-range magnetic order occurring despite a peak in the specific heat at $T^{*} =1.2$ K. Rather, magnetic diffuse scattering occurs which corresponds to short-range magnetic correlations occurring across two unit cells. The specific heat remains large as $T\sim0$ K...
Topics: Strongly Correlated Electrons, Materials Science, Condensed Matter
Source: http://arxiv.org/abs/1408.6576
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61
Sep 19, 2013
09/13
by
K. Gofryk; A. S. Sefat; M. A. McGuire; B. C. Sales; D. Mandrus; T. Imai; J. D. Thompson; E. D. Bauer; F. Ronning
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We report the temperature dependence of the low-temperature specific heat down to 400 mK of the electron-doped Ba(Fe$_{0.92}$Co$_{0.08}$)$_{2}$As$_{2}$ superconductors. We have measured two samples extracted from the same batch: first sample has been measured just after preparation with no additional heat treatment. The sample shows $T_{c}$=20 K, residual specific heat $\gamma_{0}$=3.6 mJ/mol K$^{2}$ and a Schottky-like contribution at low temperatures. A second sample has been annealed at 800...
Source: http://arxiv.org/abs/1009.0954v1
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49
Sep 21, 2013
09/13
by
C. H. Wang; J. M. Lawrence; E. D. Bauer; K. Kothapalli; J. S. Gardner; F. Ronning; K. Gofryk; J. D. Thompson; H. Nakotte; F. Trouw
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Magnetic susceptibility results for single crystals of the new cubic compounds UT$_2$Al$_{20}$ (T=Mn, V, and Mo) are reported. Magnetization, specific heat, resistivity, and neutron diffraction results for a single crystal and neutron diffraction and inelastic spectra for a powder sample are reported for UMn$_2$Al$_{20}$. For T = V and Mo, temperature independent Pauli paramagnetism is observed. For UMn$_2$Al$_{20}$, a ferromagnetic transition is observed in the magnetic susceptibility at $T_c$...
Source: http://arxiv.org/abs/1008.2235v1
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96
Sep 22, 2013
09/13
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K. Gofryk; F. Ronning; J. -X. Zhu; M. N. Ou; P. H. Tobash; S. S. Stoyko; X. Lu; A. Mar; T. Park; E. D. Bauer; J. D. Thompson; Z. Fisk
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We report a globally reversible effect of electronic tuning on the magnetic phase diagram in CeCoIn_{5} driven by electron (Pt and Sn) and hole (Cd, Hg) doping. Consequently, we are able to extract the superconducting pair breaking component for hole and electron dopants with pressure and co-doping studies, respectively. We find that these nominally non-magnetic dopants have a remarkably weak pair breaking effect for a d-wave superconductor. The pair breaking is weaker for hole dopants, which...
Source: http://arxiv.org/abs/1210.0672v1
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52
Sep 21, 2013
09/13
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Dong-Jin Jang; A. B. Vorontsov; I. Vekhter; K. Gofryk; Z. Yang; S. Ju; J. B. Hong; J. H. Han; Y. S. Kwon; F. Ronning; J. D. Thompson; Tuson Park
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We present low-temperature specific heat of the electron-doped Ba(Fe$_{0.9}$Co$_{0.1}$)$_{2}$As$_{2}$, which does not show any indication of an upturn down to 400 mK, the lowest measuring temperature. The lack of a Schottky-like feature at low temperatures or in magnetic fields up to 9 Tesla enables us to identify enhanced low-temperature quasiparticle excitations and to study anisotropy in the linear term of the specific heat. Our results can not be explained by a single or multiple isotropic...
Source: http://arxiv.org/abs/1011.4808v1
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52
Sep 21, 2013
09/13
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C. H. Wang; J. M. Lawrence; A. D. Christianson; S. Chang; K. Gofryk; E. D. Bauer; F. Ronning; J. D. Thompson; K. J. McClellan; J. A. Rodriguez-Rivera; J. W. Lynn
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We have performed magnetic susceptibility, specific heat, resistivity, and inelastic neutron scattering measurements on a single crystal of the heavy Fermion compound Ce(Ni$_{0.935}$Pd$_{0.065}$)$_2$Ge$_2$, which is believed to be close to a quantum critical point (QCP) at T = 0. At lowest temperature(1.8-3.5 K), the magnetic susceptibility behaves as $\chi(T)-\chi (0)$ $\propto$ $T^{-1/6}$ with $\chi (0) = 0.032 \times 10^{-6}$ m$^3$/mole (0.0025 emu/mole). For $T
Source: http://arxiv.org/abs/1104.0203v1
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48
Sep 23, 2013
09/13
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J. Qi; T. Durakiewicz; S. A. Trugman; J. -X. Zhu; P. S. Riseborough; R. Baumbach; E. D. Bauer; K. Gofryk; J. -Q. Meng; J. J. Joyce; A. J. Taylor; R. P. Prasankumar
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Ultrafast optical spectroscopy is used to study the antiferromagnetic f-electron system USb2. We observe the opening of two charge gaps at low temperatures (
Source: http://arxiv.org/abs/1303.2694v1
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97
Sep 17, 2013
09/13
by
C. H. Wang; J. M. Lawrence; A. D. Christianson; E. A. Goremychkin; V. R. Fanelli; K. Gofryk; E. D. Bauer; F. Ronning; J. D. Thompson; N. R. de Souza; A. I. Kolesnikov; K. C. Littrell
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We report measurements of inelastic neutron scattering, magnetic susceptibility, magnetization, and the magnetic field dependence of the specific heat for the heavy Fermion compounds Ce$_3$In and Ce$_3$Sn. The neutron scattering results show that the excited crystal field levels have energies $E_1$ = 13.2 meV, $E_2$ = 44.8 meV for Ce$_3$In and $E_1$ = 18.5 meV, $E_2$ = 36.1 meV for Ce$_3$Sn. The Kondo temperature deduced from the quasielastic linewidth is 17 K for Ce$_3$In and 40 K for...
Source: http://arxiv.org/abs/1003.3462v1
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43
Sep 20, 2013
09/13
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T. Klimczuk; H. C. Walker; R. Springell; A. B. Shick; A. H. Hill; P. Gaczynski; K. Gofryk; S. A. J. Kimber; C. Ritter; E. Colineau; J. -C. Griveau; D. Bouexiere; R. Eloirdi; R. J. Cava; R. Caciuffo
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A neptunium analogue of the LaFeAsO tetragonal layered compound has been synthesized and characterized by a variety of experimental techniques. The occurrence of long-range magnetic order below a critical temperature T_N = 57 K is suggested by anomalies in the temperature-dependent magnetic susceptibility, electrical resistivity, Hall coefficient, and specific heat curves. Below T_N, powder neutron diffraction measurements reveal an antiferromagnetic structure of the Np sublattice, with an...
Source: http://arxiv.org/abs/1205.0438v1
7
7.0
Jun 30, 2018
06/18
by
C. H. Wang; L. Poudel; A. E. Taylor; J. M. Lawrence; A. D. Christianson; S. Chang; J. A. Rodriguez-Rivera; J. W. Lynn; A. A. Podlesnyak; 1 G. Ehlers; R. E. Baumbach; E. D. Bauer; K. Gofryk; F. Ronning; K. J. McClellan; J. D. Thompson
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Electric resistivity, specific heat, magnetic susceptibility, and inelastic neutron scattering experiments were performed on a single crystal of the heavy fermion compound Ce(Ni$_{0.935}$Pd$_{0.065}$)$_2$Ge$_2$ in order to study the spin fluctuations near an antiferromagnetic (AF) quantum critical point (QCP). The resistivity and the specific heat coefficient for $T \leq$ 1 K exhibit the power law behavior expected for a 3D itinerant AF QCP ($\rho(T) \sim T^{3/2}$ and $\gamma(T) \sim \gamma_0 -...
Topics: Strongly Correlated Electrons, Condensed Matter
Source: http://arxiv.org/abs/1411.3689