Heavy non-Fermi-liquid behavior in nearness to ferromagnetism in Th1−x Ux Cu2 Si2s

Abstract

${\mathrm{Th}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{U}}_{\mathrm{x}}$ ${\mathrm{Cu}}_2$ ${\mathrm{Si}}_2$ compounds have been investigated by means of specific heat, susceptibility, magnetization, and resistivity measurements. Samples with x⩾0.15 are ferromagnetic.${\mathrm{mTh}}_{0.85}$ ${\mathrm{U}}_{0.15}$ ${\mathrm{Cu}}_2$ ${\mathrm{Si}}_2$ and ${\mathrm{Th}}_{0.8}$ ${\mathrm{U}}_{0.2}$ ${\mathrm{Cu}}_2$ ${\mathrm{Si}}_2$ show enhanced values for C/T at low temperatures (≈460 mJ/U mol ${\mathrm{K}}^2$ for x=0.2). The specific heat of samples that exhibit no long-range order (x⩽0.1) can be described by C/T∝-ln(T). This divergence is characteristic of non-Fermi-liquid (nFl) systems. The results are discussed in regard to the current investigations on non-Fermi liquids. One interpretation of non-Fermi-liquid behavior is a T=0 instability in nearness to magnetism. Our data indicate that this is a system that displays C/T∝ln T near to ferromagnetism.