B. Andraka

High magnetic field phase diagram of PrOs4Sb12

The magnetic phase diagram of PrOs4Sb12 has been investigated by specific heat measurements between 8 and 32 T. A new Schottky anomaly, due to excitations between two lowest crystalline-electric-field (CEF) singlets, has been found for both H parallel (100) and H parallel (110) above the field where the field-induced ordered phase (FIOP) is suppressed. The constructed H-T phase diagram shows weak magnetic anisotropy and implies a crossing of the two CEF levels at about 8-9 T for both field directions. These results provide an unambiguous evidence for the Gamma(1) singlet being the CEF ground state and suggest the level crossing (involving lowest CEF levels) as the driving mechanism of FIOP.

Specific heat of the high Tc organic superconductor κ-(ET)2Cu[N(CN)2]Br

Abstract An anomally in the specific heat of κ-(ET)2Cu[N(CN)2]Br, where ET is the radical-cation donor molecule bis(ethylenedithio)tetrathiafulvalene, has been observed around Tc ∼ 11.5K, indicating bulk superconductivity in this organic charge-transfer salt. The normal-state electronic specific heat coefficient, γ = 22 ± 3 mJK-2mol was obtained by the suppression of superconductivity with a sufficiently strong magnetic field applied parallel to the crystallographic b direction. The ratio of the specific heat discontinuity ΔC to γT indicates strong coupling. Comparisons with other ET-based organic superconductors are made.

Glassy Spin Dynamics in Non-Fermi-Liquid UCu5xPdx, x = 1.0 and 1.5

Local f-electron spin dynamics in the non-Fermi-liquid heavy-fermion alloys UCu5-xPdx, x = 1.0 and 1.5, have been studied using muon spin-lattice relaxation. The sample-averaged asymmetry function G(t) indicates strongly inhomogeneous spin fluctuations and exhibits the scaling G(t,H) = G(t/H(gamma)) expected from glassy dynamics. At 0.05 K gamma(x = 1.0) = 0.35+/-0.1, but gamma(x = 1.5) = 0.7+/-0.1. This is in contrast to inelastic neutron scattering results, which yield gamma = 0.33 for both concentrations. There is no sign of static magnetism approximately greater than 10(-3)(B)/U ion in either material above 0.05 K. Our results strongly suggest that both alloys are quantum spin glasses.

Magnetism and heavy fermions in YbRhSn and YbPtSn

Isostructural YbRhSn and YbPtSn were studied by specific heat, electrical resistivity, and magnetoresistance. Both compounds order antiferromagnetically below 2 and 3.5 K, respectively. Above 4 K, they display a number of remarkable similarities including Kondo-like resistivity and large negative magnetoresistance. Scaling analysis of this magnetoresistance shows that it is due to the suppression of Kondo scattering in YbRhSn but has a ferromagnetic spin fluctuation character in YbPtSn. The heavy fermion state was confirmed in YbRhSn by low temperature specific heat measurements yielding γ of about 1200 mJ/K2 mol. γ for YbPtSn is of order 100 mJ/K2 mol only.

Effect of Th-substitution in a new dense-Kondo compound UCu5Al

Abstract We have investigated magnetic, electrical, and thermodynamic properties of a new system U1−xThxCu5Al. We have found that these alloys are antiferromagnetically ordered Kondo systems and exhibit moderate heavy fermion behaviour at low temperatures.

Anomalous low-temperature state of a possible Kondo semimetal Ce Os 4 Sb 12 : Magnetic field and La impurity study

Specific heat in magnetic fields to

High-field phase diagram of the Haldane-gap antiferromagnet Ni(C5H14N2)2N3(PF6)

14\phantom{\rule{0.3em}{0ex}}\mathrm{T}

Specific heat of the S = 1 spin-dimer antiferromagnet Ba 3 Mn 2 O 8 in high magnetic fields

, magnetic susceptibility and electrical resistivity for single crystalline samples of

Specific Heat of Ce0.8La0.2Al3 in Magnetic Fields: A Test of the Anisotropic Kondo Picture

{\mathrm{Ce}}_{1\ensuremath{-}x}{\mathrm{La}}_{x}{\mathrm{Os}}_{4}{\mathrm{Sb}}_{12}