Nonequilibrium low temperature phase in pyrochlore iridate Y$_2$Ir$_2$O$_7$: Possibility of glass-like dynamics

Abstract

Geometrical frustration and spin-orbit coupling effect together play vital role to influence properties in pyrochlore based iridium oxides. Here we have investigated detailed structural, magnetic, thermodynamic and transport properties of pyrochlore iridate Y$_2$Ir$_2$O$_7$. Magnetization data show onset of magnetic irreversibility around temperature $T_{irr}$ $\sim$ 160 K, however, no sign of long-range type ferromagnetic ordering is observed below $T_{irr}$. Specific heat data show no visible anomaly across $T_{irr}$, and the analysis of data indicate sizable density of states across Fermi level. Temperature dependent x-ray diffraction measurements show no change in structural symmetry down to low temperature. The material, on the other hand, shows significant relaxation and aging behavior similar to glassy dynamics. The electronic charge transport in this highly insulating system is found to follow power law dependence with temperature. The material shows negative magnetoresistance which is explained with quantum interference effect.