Specific heat of UPd2Au3: Evidence for an unusual heavy-fermion state.

Abstract

Low-temperature specific heat and magnetic susceptibility are reported for ${\mathrm{UPd}}_{5\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Au}}_{\mathit{x}}$ alloys, for 2.5x3.2 and x=1. These low-temperature properties reflect a competition between ferromagnetic and antiferromagnetic interactions between U moments. ${\mathrm{UPd}}_{2}$${\mathrm{Au}}_{3}$ orders antiferromagnetically at 3 K. Between 5 and at least 14 K, its C/T is proportional to ${\mathit{T}}^{2}$ with a large value of the C/T intercept ${\ensuremath{\gamma}}_{\mathit{H}}$ of about 670 mJ/${\mathrm{K}}^{2}$ and a slope 3 mJ/${\mathrm{K}}^{4}$ mol. Below ${\mathit{T}}_{\mathit{N}}$, its specific heat has a magnon-derived ${\mathit{T}}^{3}$ term and a linear term (${\ensuremath{\gamma}}_{\mathit{LT}}$), ${\ensuremath{\gamma}}_{\mathit{L}}$=500 mJ/${\mathrm{K}}^{2}$ mol. Both values of ${\ensuremath{\gamma}}_{\mathit{L}}$ and ${\ensuremath{\gamma}}_{\mathit{H}}$ place this alloy into a heavy-fermion category. \textcopyright{} 1996 The American Physical Society.