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

TL;DR

This study investigates the magnetic and electronic properties of Nd2Ir2O7, revealing complex magnetic ordering and suggesting it resides near the boundary of a Dirac semimetal phase without a true metal-insulator transition.

Contribution

It provides detailed experimental insights into the magnetic ground state and electronic behavior of Nd2Ir2O7, highlighting its position in the topological phase diagram.

Findings

Hysteretic magnetization below 120 K

Resistivity increase below 8 K

Absence of a true metal-insulator transition

Abstract

We report a combined muon spin relaxation/rotation, bulk magnetization, neutron scattering, and transport study of the electronic properties of the pyrochlore iridate 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. Zero field muon spin relaxation measurements show that the hysteretic magnetization is driven by a transition to a magnetically disordered state, and that below 8 K a complex magnetically ordered ground state sets in, as evidenced by the onset of heavily damped spontaneous muon precession. Our measurements point toward the absence of a true metal-to-insulator phase transition in this material and suggest that Nd2Ir2O7 lies either within or on the metallic side of the boundary of the Dirac semimetal regime within its topological phase diagram.