LOW-TEMPERATURE SPECIFIC-HEAT OF UCU5-XPDX - A TEST FOR NON-FERMI-LIQUID THEORY

Recent theoretical works make clear predictions for the low-temperatur e properties of non-Fermi-liquid (NFL) systems. We present specific-he at data for the NR. material UCu3.5Pd1.5 down to 0.075 K (a factor of 4 lower in temperature than the previously reported data) which allows a test of the competing theories. The theory of Moriya and Takimoto [ J. Phys. Sec. Jpn. 64, 960 (1995)] which predicts C/T proportional to - ln T followed by, at lowest temperatures, C/T proportional to: 1 - r oot T, is consistent with the data. Additional low-temperature specifi c-heat and ac susceptibility data on UCu4Pd and UCuS4.2Pd0.8 are prese nted which suggest that the former still exhibits magnetism similar to the latter. Surprisingly, UCu3.5Pd1.5 also shows a magnetic transitio n via ac susceptibility at a sufficiently low temperature (similar to 0.12 K) that the influence on the specific heat is not entirely clear by the lowest temperature of the measurement. The magnetic behavior, i ncluding the frequency dependence of the peak in the ac susceptibility , is in qualitative agreement with Griffiths' [Phys. Rev. Lett. 23, 17 (1969)] phases idea of Castro Neto et nl. [cond-mat/9710123, Phys. Re v. Lett. (to be published)]. [S0163-1829(98)50240-8].