Giant Magnetoresistance in an all-oxide spacerless junction

We report the fabrication of an oxide-specific type of magnetoresistive junction, which is a ferromagnetic bilayer. Both electrodes are high spin-polarization oxides: magnetite (Fe3O4) and manganite (La0.7Sr0.3MnO3). Negligible magnetic coupling between both ferromagnetic electrodes is realised, which allows to obtain parallel and antiparallel magnetic configurations of the electrodes when sweeping the applied magnetic field. The structure exhibits negative giant magnetoresistance (GMR) at low temperatures. This negative MR shows that both electrodes stay spin-polarized at the interface and have opposite spin polarizations, i.e. the Fe3O4 layer has a negative spin polarization at low temperature. Maximum GMR (-5%) is obtained at 55K.