The specific heat of UCd11 has been investigated in magnetic fields up to 16 T and in the temperature range 0.3510 K. In addition to the well-known 5-K magnetic transition, another anomaly is observed below 2 K in fields larger than 10 T. This anomaly can be related to the previously reported signature in the temperature-dependent resistivity under pressure. Furthermore, the magnetic fields do not affect the high-temperature specific heat (above the 5-K transition). The latter observation is discussed in relation to the origin of the extremely large electronic effective mass of UCd11. © 1991 The American Physical Society.

We have discovered a new heavy-fermion system, CeCu6, with a large susceptibility (=0.027 emu/mole G at 1.5 K) and a large, temperature-dependent specific heat below 10 K that is 840 mJ/mole K2 at 1.8 K and extrapolates to 1.6 J/mole K2 at T=0 in analogy with CeAl3. High-field specific-heat measurements agree almost perfectly with a narrow-band picture first proposed for UBe13. © 1984 The American Physical Society.

We report the first thorough characterization of single crystals of CeCu2Si2. Measurements on these flux-grown crystals, which are not superconducting above 0.050 K, include ac susceptibility, resistivity, Hall effect, and specific heat. A review of other measurements is given, and the implications of our single-crystal data are discussed. Specifically, our data are consistent with superconductivity in CeCu2Si2 being destroyed by having too low a Kondo temperature, although TKondo is not found to be inversely proportional to as previously claimed. The entropy associated with the low-temperature specific-heat anomaly is found to be only 0.66R ln2, in contrast to the previous result of R ln2 for polycrystalline material. The lack of superconductivity in our single crystals does not appear to be due to poor stoichiometry to +5%, as proposed previously for single crystals grown by a Bridgman technique. The possibility of charge-density waves suppressing superconductivity in strain-free material is discussed, although no experimental verification is found. © 1983 The American Physical Society.

Convincing evidence has been discovered for bulk superconductivity in UPt3 at 0.54 K based on specific-heat, resistance, and ac susceptibility measurements. In addition, new evidence is presented that indicates that UPt3 is a spin-fluctuation system. If true, this is the first coexistent superconductor spin-fluctuation system. © 1984 The American Physical Society.

The specific heat of U Cd11 was measured in magnetic fields to 27 T. Besides the antiferromagnetic transition, there is a second transition that can be clearly resolved in fields between 14 and 20 T. This second transition (at Tm) extrapolates to a broad shoulder in CT in zero field. The two lines of transitions cross somewhere between 20 and 23 T. Tm displays unusually weak dependence on the strength of the magnetic field. Our results argue for the intrinsic origin of this "hidden" transition. © 2005 American Institute of Physics.

We have investigated the effects of impurities on the heavy fermion system U2Zn17. The Neél temperature of 9.7 K in pure U2Zn17 is strongly depressed to below 1.5 K with 2% Cu (on the Zn site) or 20% Th (on the U site). The electronic specific heat coefficient is practically independent of impurity concentration above any magnetic ordering temperature. © 1986.

The compound UAl2 exhibits ferromagnetic spin fluctuations at low temperatures. When 15 at.% La is substituted for U in UAl2, we find the low-temperature magnetic susceptibility increases by more than a factor of 2. We have also measured specific heat on this sample at low temperatures. We find that the electronic density of states has increased by 60% and the spin-fluctuation contribution has increased by a factor of 2. We conclude from these measurements that the Stoner enhancement factor has increased by 30% and the spin-fluctuation temperature has increased by 50% as compared with UAl2. In addition, we have measured the electrical resistivity of U0.85La0.15Al2. We find the residual resistivity to be approximately an order of magnitude larger than that of UAl2. We attribute this effect to the breaking of UU bonds by the La atoms. © 1983 The American Physical Society.

We have prepared single crystals of NpBe13, Np0.68U0.32Be13, and PuBe13 and measured their resistivity, susceptibility, and specific heat down to low temperatures. NpBe13 has an itinerant-electron magnetic transition at 3.4 K, with a large temperature-dependent specific heat above this transition that is quite similar to that observed in the heavy-fermion superconductor UBe13 and a (T=0) of approximately 900 mJ/mole K2. PuBe13 may be described as a Kondo-type system, with certain inconsistencies. The data are compared to results for UBe13 and are consistent with a narrow f band at the Fermi energy in UBe13 moving lower in energy with the addition of f electrons in heavier actinide elements to create a Kondo resonance by PuBe13. © 1984 The American Physical Society.

Results of measurements of the electrical resistivity ρ{variant} between 0.04 and 1 K and the specific heat cp between 0.06 and 1 K of annealed polycrystalline CeCu6 are reported. ρ{variant} varies proportional to T2 below 0.1 K but is linear in T above 0.6 K. The specific heat is proportional to T below 0.5 K and the electronic specific-heat parameter γ = 1.53 J mole K2. © 1985.

Fluid capacity measurements on the heavy formion superconductor UPt3 in an 11T magnetic field show that aboveapproximately 7 K, UPt3 behaves like the spin fluctuation compounds UAl2 and TiB2. Magnetoresistance measurements on UPt3 at 1.2 K also yield results similar to UAl2 in contrast to the other heavy fermion superconductors CeCu3Si3 and UBe1, which show a magneticresistance effect of opposite sign. Thus, experimental results permit continued speculation of triplet superconductivity in UPt3. © 1984 Elsevier Science Publishers B.V.