Nonmagnetic Ground State of Rutile RuO$_2$ from Diffusion Quantum Monte Carlo

TL;DR

This study uses advanced quantum Monte Carlo methods to determine that pristine bulk RuO$_2$ is nonmagnetic, but strain can induce antiferromagnetism, clarifying previous conflicting predictions and experiments.

Contribution

The paper provides the first diffusion quantum Monte Carlo evidence that pristine RuO$_2$ is nonmagnetic and identifies strain as a tuning parameter for magnetic states.

Findings

Pristine RuO$_2$ is nonmagnetic.

Strain stabilizes antiferromagnetism in RuO$_2$.

Results reconcile conflicting experimental reports.

Abstract

Rutile RuO$_2$ has been proposed as an altermagnet, but its bulk magnetic ground state is still under debate because density-functional calculations give conflicting predictions. Using fixed-node diffusion quantum Monte Carlo, we find that stoichiometric bulk RuO$_2$ is nonmagnetic in the pristine structure, lying 23(9) meV per formula unit below the lowest antiferromagnetic state considered. A 3$\%$ compressive strain instead stabilizes antiferromagnetism, placing RuO$_2$ near a strain-tunable magnetic instability and helping reconcile apparently conflicting experimental reports.