Spin injection from epitaxial Fe3O4 films to ZnO films

The fully epitaxial Fe3O4/ZnO heterostructures were fabricated by reactive dc sputtering (Fe3O4) and rf sputtering (ZnO) on c-Al2O3 substrates. The epitaxial relationship is verified to be Fe3O4(111)<110>(parallel sign)ZnO(0002)<1120> by φ scans. The nonlinear and rectifying properties of I-V curves were observed in the heterostructures. The transport mechanism across the interface between Fe3O4 and ZnO is thermal emission and the Schottky barrier is calculated to be 0.51 eV. The magnetoresistance of the heterostructures is symmetric and depends on current. The spin polarization of the transport electrons from Fe3O4 into ZnO is determined to be 28.5% at 30 K.