Magnetization and Hall effect studies on the pyrochlore iridate Nd2Ir2O7

We present magnetization and Hall effect measurements on the pyrochlore iridate Nd2Ir2O7. Previous muon spin rotation measurements have shown that the system undergoes an unusual transition at T-M approximate to 110 K into a magnetic phase lacking long-range order, followed by a transition at T-LRO approximate to 6 K into a state with long-range magnetic order. We observe a small remnant magnetization when cycling through a zero magnetic field at temperatures below T-M. Below T-LRO, this remnant magnetization increases sharply, and additional hysteresis effects appear at a higher field B-c = 2.5 T, while the Hall resistance develops a nonmonotonic and hysteretic magnetic field dependence, with a maximum at B-c and signatures of an anomalous Hall effect. The dependence on field sweep direction demonstrates a nontrivial transition into a magnetically ordered state with properties paralleling those of known spin-ice systems and suggests a spin reorientation transition across the metal-insulator transition in the A-227 series. DOI: 10.1103/PhysRevB.87.060403