We have investigated the origins of enhanced saturated magnetic moment and strong strain-dependent magnetic anisotropy in epitaxial films of the transition-metal oxide SrRuO${}_3$. We find evidence for an enhancement of the carrier concentration and the stabilization of high-spin Ru${}^{4+}$. Through x-ray magnetic circular dichroism measurements, we also observe a strain-dependent enhancement of the out-of-plane orbital magnetic moment. Such an enhancement is consistent with the universal out-of-plane anisotropy axis shown to occur in films in a variety of different crystallographic orientations. We explain all these effects in terms of an anisotropic reduction in the crystal field resulting from anisotropically reduced orbital overlap in distorted films.

• Received 7 November 2011

DOI:https://doi.org/10.1103/PhysRevB.85.134429