Effects of Magnetovolume and Spin-orbit Coupling in the Ferromagnetic Cubic Perovskite BaRuO3

TL;DR

This study uses first principles calculations to explore the ferromagnetism in cubic BaRuO3, revealing the roles of van Hove singularities, magnetovolume effects, and spin-orbit coupling in its magnetic properties.

Contribution

It provides a detailed theoretical analysis of the magnetic behavior of BaRuO3, highlighting the combined effects of electronic structure, magnetovolume, and spin-orbit coupling, which were not previously characterized.

Findings

Van Hove singularities cause high magnetovolume effects.

Spin-orbit coupling reduces the magnetic moment by 10%.

Ferromagnetism is driven by Stoner instability.

Abstract

BaRuO3 having five different crystal structures has been synthesized by varying the pressure while sintering. Contrary to the other phases being nonmagnetic, the cubic perovskite phase synthesized recently shows an itinerant ferromagnetic character. We investigated this ferromagnetic BaRuO3 using first principles calculations. A few van Hove singularities appear around the Fermi energy, causing unusually high magnetovolume effects of $\Delta M/\Delta a$ ~ 4.3 $\mu_B$/\AA as well as a Stoner instability [IN(0) ~ 1.2]. At the optimized lattice parameter a, the magnetic moment M is 1.01 $\mu_B$ in the local spin density approximation. When spin-orbit coupling is included, the topologies of some Fermi surfaces are altered, and the net moment is reduced by 10% to a value very close to the experimentally observed value of ~ 0.8 $\mu_B$. Our results indicate that this ferromagnetism is induced by the Stoner instability, but the combined effects of the p-d hybridization, the magnetovolume, and the spin-orbit coupling determine the net moment. In addition, we briefly discuss the results of the tight-binding Wannier function technique.