Investigation into the role of the orbital moment in a series of isostructural weak ferromagnets

TL;DR

This study explores how the orbital magnetic moment varies in a series of isostructural weak ferromagnets, revealing significant effects of spin-orbit coupling on magnetic and lattice properties through combined experimental and theoretical methods.

Contribution

It demonstrates the importance of spin-orbit interaction in weak ferromagnets and validates first-principles calculations for predicting complex magnetic behaviors.

Findings

Large orbital moments in Co-based compound.

Coupling between magnetic and lattice degrees of freedom.

Significant magnetostrictive effects observed.

Abstract

The orbital contribution to the magnetic moment of the transition metal ion in the isostructural weak ferromagnets ACO$_3$ (A=Mn,Co,Ni) and FeBO$_3$ was investigated by a combination of first-principles calculations, non-resonant x-ray magnetic scattering and x-ray magnetic circular dichroism. A non-trivial evolution of the orbital moment as a function of the $3d$ orbitals filling is revealed, with an anomalously large value found in the Co member of the family. Here, the coupling between magnetic and lattice degrees of freedom produced by the spin-orbit interaction results in a large single-ion anisotropy and a peculiar magnetic-moment-induced electron cloud distortion, evidenced by the appearance of a subtle scattering amplitude at space group-forbidden reflections and significant magnetostrictive effects. Our results, which complement a previous investigation on the sign of the Dzyaloshinskii$-$Moriya interaction across the series, highlight the importance of spin-orbit coupling in the physics of weak ferromagnets and prove the ability of modern first-principles calculations to predict the properties of materials where the Dzyaloshinskii$-$Moriya interaction is a fundamental ingredient of the magnetic Hamiltonian.