Muon spin rotation and non-Fermi liquid behavior in UCu 4Pd

Abstract

Muon spin rotation and relaxation (μSR) experiments have been carrried out on the non-Fermi liquid (NFL) heavy-fermion compound UCu 4Pd. Transverse-field μSR line widths indicate that the U-ion susceptibility is inhomogeneous and in good agreement with predictions of disorder-driven NFL mechanisms. The inhomogeneity seems to be remarkably independent of the exact amount of structural disorder. Longitudinal-field experiments yield muon spin-lattice relaxation rates which are two orders of magnitude faster than estimates from a single-ion ‘Kondo disorder’ model. This suggests a cooperative rather than a single-ion NFL mechanism. No evidence is found for freezing of more than a few percent of U-ion moments in UCu 4Pd above 100 mK.