Perovskite oxide superlattices: Magnetotransport and magnetic properties

We have fabricated perovskite superlattices consisting of two ferromagnetic metallic oxides: ${\mathrm{La}}_{0.67}$ ${\mathrm{Ca}}_{0.33}$Mn${\mathrm{O}}_3$ (LCMO) and SrRu${\mathrm{O}}_3$ (SRO). We have investigated the magnetotransport and magnetic properties of a series of samples, in which the layer thickness of LCMO is fixed and that of SRO varied from 0 to 20 unit cells. The magnetoresistance ratio in a superlattice can be increased by a factor of 3 at low temperatures over the MR ratio in pure LCMO film. This substantial enhancement is most likely caused by the interface spin-dependent scattering. The superlattice structure also increases $T_c$ of LCMO by introducing a biaxial tension, and induces two consecutive switchings of magnetic easy axis direction with increasing SRO thickness.