Magnetic-field-induced reentrance of Fermi-liquid behavior and spin-lattice relaxation rates in YbCu_{5-x}Au_x

TL;DR

This paper explains anomalies in magnetic susceptibility and spin-lattice relaxation rates in YbCu_{5-x}Au_x using a fermion condensation quantum phase transition model, revealing a field-induced reentrance of Fermi-liquid behavior.

Contribution

It introduces a theoretical framework based on FCQPT to unify the understanding of magnetic and relaxation anomalies in heavy fermion compounds.

Findings

Anomalies in susceptibility and relaxation rates are explained by quasiparticle effective mass scaling.

Field-induced reentrance of Fermi-liquid behavior is demonstrated.

The approach clarifies scaling in magnetoresistance of YbRh_2Si_2.

Abstract

A strong departure from Landau-Fermi liquid (LFL) behavior have been recently revealed in observed anomalies in both the magnetic susceptibility $\chi$ and the muon and $\rm ^{63}Cu$ nuclear spin-lattice relaxation rates $1/T_1$ of ${\rm {YbCu_{5-x}Au_x}}$ ($x=0.6$). We show that the above anomalies along with magnetic-field-induced reentrance of LFL properties are indeed determined by the scaling behavior of the quasiparticle effective mass. We obtain the scaling behavior theoretically utilizing our approach based on fermion condensation quantum phase transition (FCQPT) notion. Our theoretical analysis of experimental data on the base of FCQPT approach permits not only to explain above two experimental facts in a unified manner, but to clarify the physical reasons for a scaling behavior of the longitudinal magnetoresistance in $\rm YbRh_2Si_2$.