Current-perpendicular-to-plane magnetoresistance (CPP-MR) devices using a Co2Fe(Ga0.5Ge0.5) Heusler alloy as ferromagnetic electrodes and a Ag/Mg-Ti-O (MTO)/Ag tri-layer as a spacer are studied. A large voltage output of 16 mV with a magnetoresistance ratio of 46% and resistance-area product RpA in the parallel magnetization state of approximately 200 mΩ μm2 are obtained. The microstructure characterization reveals that upon annealing at 550 °C, nanoscale Ag channels are formed penetrating the MTO layer, which are responsible for the large MR output. At room temperature, for all the devices, RpA decreases with increasing the bias voltage Vb, which is contradictory to the conventional CPP-giant magnetoresistance devices with a current-confined-path structure, in which the RpA increases with increasing Vb. Such a Vb dependence of RpA is in accordance with the temperature dependence of RpA. These results suggest that the magneto-transport channels comprise semiconducting current confined paths, bringing new perspectives for the design and engineering of CPP-MR devices with conductive oxides-based multilayer spacers.
ASJC Scopus subject areas