Role of doped Ru in coercivity-enhanced La0.6Sr0.4MnO3 thin film studied by x-ray magnetic circular dichroism

The coercivity of La1– x Sr x MnO3 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 SrTiO3 substrate in the presence of spin-orbit interaction.