Magnetoresistance of Manganite-Cobalt Ferrite Spacerless Junctions

We report the fabrication of heteroepitaxial pseudospin-valve structure using high spin polarization oxides of CoFe₂O₄ (CFO) and La_0.7Sr_0.3MnO₃ (LSMO) as ferromagnetic electrodes. Transmission electron microscopy images revealed a 2 nm natural spacer layer at the interface between CFO and LSMO, which decoupled the two layers and permitted the observation of spin-valve effect. These heteroepitaxial spin-valve junctions showed positive magnetoresistive behavior, although CFO and LSMO are known to possess opposite spin polarization coefficients. We suggest that the abnormal magnetoresistive behavior originates from the change of spin polarization coefficient arising from the barrier layer. Our results demonstrated that naturally formed interfacial layers provide a simple route for fabricating all-oxide-based spin-valve junctions.