Magnetic order and the electronic ground state in the pyrochlore iridate Nd2Ir2O7

We report a muon spin relaxation/rotation, bulk magnetization, neutron scattering, and transport study of the electronic properties of Nd2Ir2O7. We observe the onset of strongly hysteretic behavior in the temperature-dependent magnetization below 120 K, and an abrupt increase in the temperature-dependent resistivity below 8 K. Muon spin relaxation measurements show that the hysteretic magnetization is driven by a transition to a magnetically disordered state, and below 8 K a magnetically ordered ground state sets in, as evidenced by the onset of spontaneous muon precession. Our measurements point toward the absence of a true metal-to-insulator phase transition in this material and suggest that Nd2Ir2O7 may lie within or on the metallic side of the boundary of the Dirac semimetal regime within its topological phase diagram.