Non-Fermi liquid regime in metallic pyrochlore iridates: Quantum Griffiths singularities

Abstract

We investigate the interplay of Kondo and RKKY coupling in presence of disorder by chemically substituting local moment Cr^{3+} at the Ir sublattice in the metallic Pr_{2}Ir_{2}O_{7}. We find evidence of non-Fermi liquid (NFL) behaviour in the transport and thermodynamic measurements at low temperature. Specifically, the magnetic susceptibility exhibits power law divergence at T=0. The nonanalytic temperature and magnetic-field dependence of magnetic susceptibility and the associated scaling suggest existence of a two-fluid system consisting of Kondo-screened paramagnetic metal coexisting with magnetically ordered rare regions dominated by inter-impurity interaction, similar to quantum critical Griffiths phase.