Nonequilibrium low temperature phase in pyrochlore iridate Y2Ir2O7: Possibility of glass-like dynamics

• The Y2Ir2O7 shows magnetic irreversibility below temperature 160 K.
• The material, however, does not exhibit ferromagnetism at low temperature.
• The structural symmetry is reserved throughout the temperature range.
• Magnetic relaxation and aging behavior imply nonequilibrium magnetic state.
• Nature of magnetoresistance is explained with weak localization effect.

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 Y2Ir2O7. Magnetization data show onset of magnetic irreversibility around temperature Tirr∼160K, however, no sign of long-range type ferromagnetic ordering is observed below Tirr. Specific heat data show no visible anomaly across Tirr, 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.