Susceptibility inhomogeneity and non-Fermi liquid behavior in nominally ordered UCu_4Pd

TL;DR

Muon spin rotation experiments on UCu_4Pd reveal strong low-temperature inhomogeneity in U-ion susceptibility, suggesting residual disorder influences non-Fermi liquid behavior and challenging cluster-based models.

Contribution

This study provides direct evidence of inhomogeneous susceptibility in a nominally ordered NFL compound, highlighting the role of residual disorder in NFL phenomena.

Findings

U-ion susceptibility is strongly inhomogeneous at low temperatures

Residual disorder dominates NFL behavior in UCu_4Pd

Inhomogeneity has a short correlation length (≤ 1 lattice spacing)

Abstract

Muon spin rotation experiments on a stoichiometric sample of the non-Fermi liquid (NFL) heavy-fermion compound UCu_4Pd, in which recent neutron Bragg scattering measurements are consistent with an ordered structure, indicate that the U-ion susceptibility is strongly inhomogeneous at low temperatures. This suggests that residual disorder dominates NFL behavior. The data also indicate a short correlation length (\lesssim 1 lattice spacing) for this inhomogeneity and a rapid low-temperature U-moment relaxation rate (\gtrsim 10^{12} s^{-1}), which constrain cluster-based models of NFL behavior.