Possible correlated-electron behavior from quadrupolar fluctuations in PrInAg2

The temperature dependent magnetic susceptibility; specific heat, and electrical resistivity were measured on PrInAg2. A broad peak, which is identified as a Kondo anomaly, is observed in the specific heat at similar to 0.4 K with a strongly enhanced linear contribution at lower temperatures. PrInAg2 is a Pr-based heavy-fermion compound and has one of the largest known Sommerfeld coefficients of similar to 6.5 J/mol K-2. A new type of nonmagnetic interaction between the conduction electrons and the non-Kramers doublet ground state of the Pr3+ ion be responsible for this behavior. Related features are also observed in the susceptibility and resistivity.This article is published as Yatskar, A., W. P. Beyermann, R. Movshovich, and P. C. Canfield. "Possible correlated-electron behavior from quadrupolar fluctuations in PrInA g 2." Physical review letters 77, no. 17 (1996): 3637. DOI: 10.1103/PhysRevLett.77.3637. Copyright 1996 American Physical Society. Posted with permission

Heavy-electron behavior in single-crystal YbNi2B2C

We have measured the magnetic susceptibility, specific heat, and electrical resistivity on single crystals of the intermetallic borocarbide YbNi2B2C. An enhanced linear contribution is observed in the specific heat with a Sommerfeld coefficient of 530 mJ/mol K-2, indicative of a heavy-electron system with a Kondo temperature similar to 10 K. The magnetic susceptibility, which is anisotropic and Curie-Weiss-like at high temperature, is also consistent with our interpretation of a strongly correlated ground state at low temperatures and crystal-electric-field excitations at higher temperatures. At T=1.8 K, the Wilson ratio is determined to be: 0.85 using the high-temperature effective moment. The resistivity shows a quadratic temperature dependence below 1.5 K with a T-2 coefficient of 1.2 mu Omega cm K-2. Unlike the other members of the series RNi(2)B(2)C (R=Y. Gd-Lu), YbNi2B2C does not order above our lowest measurement temperature of 0.34 K. The suppression of superconductivity in YbNi2B2C is consistent with a significantly enhanced hybridization between the conduction electrons and the 4f states.This article is published as Yatskar, A., N. K. Budraa, W. P. Beyermann, P. C. Canfield, and S. L. Bud'ko. "Heavy-electron behavior in single-crystal Yb Ni 2 B 2 C." Physical Review B 54, no. 6 (1996): R3772. DOI: 10.1103/PhysRevB.54.R3772. Copyright 1996 American Physical Society. Posted with permission

Doping and pressure study of U3Sb4Pt3

The effects of doping and pressure on the U3Sb4Pt3 system have been studied. Substitution of either trivalent yttrium or lutetium for uranium causes significant changes in the temperature dependences of the electrical resistance and of the magnitude of the linear coefficient of the specific heat γ. However, substitution of tetravalent thorium causes little change in γ, even though it affects the electrical resistance in a manner similar to that seen in the cases of lutetium and yttrium. Finally, application of hydrostatic pressures up to 16.5 kbar causes no significant change in the electronic gap deduced from the electrical resistance. © 1992

Doping and pressure study of U3Sb4Pt3

The effects of doping and pressure on the U Sb Pt system have been studied. Substitution of either trivalent yttrium or lutetium for uranium causes significant changes in the temperature dependences of the electrical resistance and of the magnitude of the linear coefficient of the specific heat γ. However, substitution of tetravalent thorium causes little change in γ, even though it affects the electrical resistance in a manner similar to that seen in the cases of lutetium and yttrium. Finally, application of hydrostatic pressures up to 16.5 kbar causes no significant change in the electronic gap deduced from the electrical resistance. © 1992. 3 4

Magnetism and heavy fermion-like behavior in the RBiPt series

Members of the RBiPt (R=Ce-Lu with the exceptions of Pm and Eu) series have been grown as single crystals. Magnetic susceptibility and electrical resistance have been measured on all members of the series, and specific heat measurements have been performed on representatives. The high temperature resistance uniformly changes from that of a small-gap semiconductor or semimetal seen in NdBiPt to that of a heavy-fermion metal seen in YbBiPt, which shows a linear coefficient of specific heat at low temperatures of 8 J/K mole. Further, the lighter rare earth members show an unusually sharp increase in their resistance associated with antiferromagnetic ordering at low temperatures.

Antiferromagnetism and enhanced specific heat in CeM2Sn2 (M = Ni, Ir, Cu, Rh, Pd and Pt)

Specific heat, DC susceptibility, and resistivity measurements on annealed, polycrystalline samples of CeM2Sn2, where M = Ni, Ir, Cu, Rh, Pd, or Pt, indicate that each of these compounds orders antiferromagnetically with transition temperatures ranging from TN = 4.1 to ≈ 0.5 K. All these materials have significant enhancements of the specific heat just before the transition, which can be as large as ∼ 3.5J/mol K2 in some cases. Provided the enhanced heat capacities above TN are associated with large effective masses, the anomalously low ordering temperature and the very large C/T suggest that TN and the Kondo temperature TK are comparable, making these materials particularly attractive for studying the interplay between these competing interactions. The susceptibility for each member of the series except M = Ir follows a Curie-Weiss behavior with a high-temperature effective moment μeff ∼ 2.5μB Ce and a small negative paramagnetic Curie temperature. © 1991

Thermal expansion of Ce3Bi4Pt3 at ambient and high pressures.

Ce3Bi4Pt3 is a cerium compound that exhibits a hybridization gap and concomitant semiconducting behavior in the coherent ground state. Using neutron powder diffraction, we have determined the variation of the lattice constant with temperature at two pressures (P=10-3 and 17.7 kbar), and determined the bulk modulus and atomic mean-square displacements for Ce3Bi4Pt3 and its normal analog, La3Bi4Pt3. The thermal expansion Δβ in Ce3Bi4Pt3 exhibits a maximum at Tmax=50 K at ambient pressure. Below 50 K, the bulk modulus ΔB is proportional to TΔβ. We apply a Grüneisen analysis, under the assumption that the free energy exhibits T/T0(V) scaling. The Grüneisen parameter deduced from the ratio ΔB/TΔβ is consistent with the value Ω=36 deduced from the pressure variation of Tmax. The analysis allows us to predict the temperature dependence of the 4f specific heat (ΔCΔβ/Ω), which thus has a maximum at 50 K and a high-temperature entropy nearly equal the expected value R ln6. We argue that the maximum at 50 K reflects an (indirect) hybridization gap of order 100 K. We show further that the lattice constant anomaly Δa0 is proportional to the effective moment Tχ; this suggests that a relationship known to be valid for antiferromagnets, namely (Tχ)/TΔC where ΔC is the specific heat, may be valid for Ce3Bi4Pt3. Finally, we show that the temperature dependence of the mean-square atomic displacements is nearly identical for Ce3Bi4Pt3 and La3Bi4Pt3 and can be fitted by a simple Debye-Waller model; hence the expansion anomaly does not affect the average lattice dynamics. © 1992 The American Physical Society

Magnetism and heavy fermion-like behavior in the RBiPt series

Members of the RBiPt (R=Ce-Lu with the exceptions of Pm and Eu) series have been grown as single crystals. Magnetic susceptibility and electrical resistance have been measured on all members of the series, and specific heat measurements have been performed on representatives. The high temperature resistance uniformly changes from that of a small-gap semiconductor or semimetal seen in NdBiPt to that of a heavy-fermion metal seen in YbBiPt, which shows a linear coefficient of specific heat at low temperatures of 8 J/K2 mole. Further, the lighter rare earth members show an unusually sharp increase in their resistance associated with antiferromagnetic ordering at low temperatures