Tuning through the quantum critical point inUCu5−xNix: Rapid variations in the specific heat

Resistivity and susceptibility near the QCP in disordered UCu5−xNix

“…Thus, the log T behavior in Áq appears to be consistent with a concentrated Kondo effect, with the reservation that the characteristic temperature determined by the resistivity is significantly smaller than that determined by the specific heat [1].…”

“…No consistent change in the lattice parameter, a 0 , or in high angle line width with annealing for 2 weeks at 750°C is evident, i.e., in contrast to the behavior observed [3] in UCu 5Àx Pd x . Although, as reported in [1], there are slight, $5%, changes in the specific heat with annealing, there is no evidence that annealing at 750°C for 2 weeks affects the order of the sample, evidenced either through changes in the lattice parameter or through measurement of the width of the high angle X-ray diffraction lines. For example, the [731] line centered at approximately 115.9°2H for the UCu 4 Ni sample shows the same line width for both unannealed and annealed samples; this is in contrast to the observed [3] sharpening of even a relatively low angle diffraction line (at 42.4°2H) in UCu 4 Pd under the same annealing treatment by 20%.…”

“…One consistency check is to compare the characteristic (putatively T K ) temperature determined from the resistivity with a characteristic temperature determined by some other measurement to see if they are consistent. The specific heat ρ μΩ Δ ρ Δ ρ ρ ρ study of UCu 5Àx Ni x [1] found that C/T varies as log T only for x QCP = 1, with a characteristic temperature of 33.3 K.…”

“…Recent investigations [2] of the electrical resistivity of UCu 5Àx Pd x have determined that the measured behavior is primarily caused by the disorder-induced localization effects, rather than by the intrinsic electronic behavior associated with the quantum critical fluctuations near the QCP. The goal of the present work is to investigate what influence strong disorder at the QCP has on both the resistivity and susceptibility of UCu 5Àx Ni x as the companion investigation to the study of the specific heat in [1].…”

“…UCu 5Àx Ni x was the focus of a recent study [1] of the non-Fermi liquid (nFl) behavior, as determined by the specific heat, of a strongly disordered system as it is tuned through its quantum critical point ('QCP'). Contrary to the case of Pd-doped UCu 5 , where the Pd experiences partial sublattice ordering on the one larger Cu sublattice site, Ni-which unlike Pd is smaller than Cu-goes equally on the four equivalent smaller Cu sites in UCu 5 at a concentration of about 25% at x QC = 1, ensuring strong lattice disorder.…”