Susceptibility inhomogeneity and non-Fermi liquid behavior in UCu_{5-x}Pt_x

TL;DR

This study investigates how disorder affects non-Fermi liquid behavior in UCu_{5-x}Pt_x alloys, revealing that increased Pt content reduces inhomogeneity and correlates with suppressed NFL anomalies, emphasizing disorder's role.

Contribution

It provides experimental evidence linking disorder-induced inhomogeneity to NFL behavior suppression in UCu_{5-x}Pt_x alloys, highlighting the importance of energy spread distribution.

Findings

Fractional spread in Knight shifts decreases with increasing x.

Energy spread remains roughly constant despite increased x.

NFL anomalies are suppressed as disorder-induced inhomogeneity decreases.

Abstract

Transverse-field muSR shifts and relaxation rates have been measured in the non-Fermi liquid (NFL) alloy system UCu_{5-x}Pt_x, x = 1.0, 1.5, and 2.5. At low temperatures the fractional spread in Knight shifts delta K/K approx deltachi/chi is gtrsim 2 for x = 1, but is only half this value for x = 1.5 and 2.5. In a disorder-driven scenario where the NFL behavior is due to a broadly distributed (Kondo or Griffiths-phase cluster) characteristic energy E, our results indicate that delta E/E_{rm av} approx (delta K/K)_{T=0} is similar for UCu_{5-x}Pd_x (x = 1 and 1.5) and UCu_4Pt, but is reduced for UCu_{5-x}Pt_x, x = 1.5 and 2.5. This reduction is due to a marked increase of E with increasing x; the spread delta E is found to be roughly independent of x. Our results correlate with the observed suppression of other NFL anomalies for x > 1 in UCu_{5-x}Pt_x but not in UCu_{5-x}Pd_x, and are further evidence for the importance of disorder in the NFL behavior of both these alloy systems.