Role of doped Ru in coercivity-enhanced La$_{0.6}$Sr$_{0.4}MnO$_3$ thin film studied by x-ray magnetic circular dichroism

TL;DR

This study investigates how Ru doping enhances coercivity in La$_{0.6}$Sr$_{0.4}$MnO$_3$ thin films by analyzing magnetic moments and orbital contributions using x-ray magnetic circular dichroism, revealing the role of local lattice distortions and spin-orbit effects.

Contribution

It provides new insights into the mechanism of coercivity enhancement through Ru doping by linking magnetic properties to local lattice distortions and spin-orbit interactions.

Findings

Ru and Mn spins are oppositely aligned.

Ru exhibits a finite orbital magnetic moment.

Lattice distortion influences magnetic moments via spin-orbit coupling.

Abstract

The coercivity of La$_{1-x}$Sr$_x$MnO$_3$ thin films can be enhanced by Ru substitution for Mn. In order to elucidate its mechanism, we performed soft x-ray absorption and magnetic circular dichroism measurements at the Ru M$_{2,3}$ and Mn L$_{2,3}$ edges. We found that the spin direction of Ru and Mn are opposite and that Ru has a finite orbital magnetic moment. Cluster-model analysis indicated that the finite orbital magnetic moment as well as the reduced spin moment of Ru result from local lattice distortion caused by epitaxial strain from the SrTiO$_3$ substrate in the presence of spin-orbit interaction.