Effect of annealing on glassy dynamics and non-Fermi liquid behavior in UCu_4Pd

TL;DR

This study investigates how annealing affects the glassy spin dynamics and non-Fermi liquid behavior in UCu_4Pd using muon spin relaxation, revealing that annealing shifts fluctuation frequencies but does not eliminate glassy dynamics.

Contribution

It provides new insights into the impact of annealing on spin fluctuations and non-Fermi liquid behavior in UCu_4Pd, showing partial modification of glassy dynamics.

Findings

Annealing reduces low-temperature relaxation rates.

Fluctuation noise shifts to higher frequencies after annealing.

Glassy spin dynamics persist despite annealing.

Abstract

Longitudinal-field muon spin relaxation (LF-muSR) experiments have been performed in unannealed and annealed samples of the heavy-fermion compound UCu_4Pd to study the effect of disorder on non-Fermi liquid behavior in this material. The muon spin relaxation functions G(t,H) obey the time-field scaling relation G(t,H) = G(t/H^gamma) previously observed in this compound. The observed scaling exponent gamma = 0.3 pm 0.1, independent of annealing. Fits of the stretched-exponential relaxation function G(t) = exp[-(Lambda t)^K] to the data yielded stretching exponentials K < 1 for all samples. Annealed samples exhibited a reduction of the relaxation rate at low temperatures, indicating that annealing shifts fluctuation noise power to higher frequencies. There was no tendency of the inhomogeneous spread in rates to decrease with annealing, which modifies but does not eliminate the glassy spin dynamics reported previously in this compound. The correlation with residual resistivity previously observed for a number of NFL heavy-electron materials is also found in the present work.