Competing interactions at the interface between ferromagnetic oxides revealed by spin-polarized neutron reflectometry

We have investigated the magnetization profiles in superlattices composed of the two ferromagnets La0.7Sr0.3MnO3 and SrRuO3 using spin-polarized neutron reflectometry. In combination with magnetometry, the neutron data indicate a noncollinear spin configuration where orientation of the Ru moments changes from in plane at the interface to out of plane deep inside the SrRuO3 layers. The spin structure originates in a competition between antiferromagnetic exchange interactions of Mn and Ru moments across the interface, and the magnetocrystalline anisotropy of the Ru moments, and it is closely related to the exchange spring structures previously observed in multilayers composed of ferromagnetic elements and alloys.