Magnetization and Hall effect studies on the pyrochlore iridate Nd2Ir2O7

We present magnetization and Hall effect measurements on the pyrochlore iridate Nd 2 Ir 2 O 7 . Previous muon spin rotation measurements have shown that the system undergoes an unusual transition at T M ≈110 K into a magnetic phase lacking long-range order, followed by a transition at T LRO ≈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