Noncollinear magnetism and spin-orbit coupling in 5d pyrochlore oxide Cd2Os2O7

TL;DR

This study uses density-functional theory to explore how noncollinear magnetism and spin-orbit coupling influence the electronic phases of Cd2Os2O7, revealing stable magnetic order and a pseudogap near phase transitions.

Contribution

It demonstrates the stability of all-in/all-out magnetic order over a range of interaction strengths and highlights the role of spin-orbit coupling in this stability.

Findings

All-in/all-out magnetic order is stable across a wide U range.

Spin-orbit coupling induces easy-axis anisotropy crucial for magnetic stability.

A pseudogap appears near the antiferromagnetic metal-insulator transition.

Abstract

We investigated the electronic and magnetic properties of the pyrochlore oxide Cd$_2$Os$_2$O$_7$ using the density-functional theory plus on-site repulsion ($U$) method, and depict the ground-state phase diagram with respect to $U$. We conclude that the all-in/all-out non-collinear magnetic order is stable in a wide range of $U$. We also show that the easy-axis anisotropy arising from the spin-orbit (SO) coupling plays a significant role in stabilizing the all-in/all-out magnetic order. A \textit{pseudo gap} was observed near the transition between the antiferromagnetic metallic and insulating phases. Finally, we discuss possible origins of the peculiar low-temperature($T$) properties observed in experiments.