Magnetism and electronic structure of La2ZnIrO6 and La2MgIrO6: candidate Jeff =1/2 Mott insulators

TL;DR

This study investigates the magnetic and electronic properties of La2ZnIrO6 and La2MgIrO6, revealing their nature as Jeff=1/2 Mott insulators and highlighting the roles of spin-orbit coupling and Coulomb interactions.

Contribution

It provides the first detailed experimental and theoretical analysis of these double perovskites, demonstrating their Jeff=1/2 Mott insulating behavior and complex magnetic states.

Findings

La2ZnIrO6 exhibits weak ferromagnetism due to canted antiferromagnetism.

La2MgIrO6 shows antiferromagnetic behavior with predicted but unobserved canting.

Both compounds are confirmed as Jeff=1/2 Mott insulators.

Abstract

We study experimentally and theoretically the electronic and magnetic properties of two insulating double perovskites that show similar atomic and electronic structure, but different magnetic properties. In magnetization measurements, La2ZnIrO6 displays weak ferromagnetic behavior below 7.5 K whereas La2MgIrO6 shows antiferromagnetic behavior (AFM) below TN = 12 K. Electronic structure calculations find that the weak ferromagnetic behavior observed in La2ZnIrO6 is in fact due to canted antiferromagnetism. The calculations also predict canted antiferromagnetic behavior in La2MgIrO6, but intriguingly this was not observed. Neutron diffraction measurements confirm the essentially antiferromagnetic behavior of both systems, but lack the sensitivity to resolve the small (0.22 {\mu}B/Ir) ferromagnetic component in La2ZnIrO6. Overall, the results presented here indicate the crucial role of spin-orbit coupling (SOC) and the on-site Coulomb repulsion on the magnetic, transport, and thermodynamic properties of both compounds. The electronic structure calculations show that both compounds, like Sr2IrO4, are Jeff = 1/2 Mott insulators. Our present findings suggest that La2ZnIrO6 and La2MgIrO6 provide a new playground to study the interplay between SOC and on-site Coulomb repulsion in a 5d transition metal oxide.