Enhanced Spin Injection into ZnO Semiconductor Measured by Magnetoresistance

We prepare 2×(NiFe/CoZnO)/ZnO/(CoZnO/Co)×2 spin valve structures used for spin injection by sputtering and photolithography. In the junctions, the free magnetic layer 2×(NiFe/CoZnO) and the fixed magnetic layer (CoZnO/Co)×2 are used to realize the spin valve functions in the external switch magnetic field. Since the wide gap semiconductor ZnO layer is located between the two magnetic semiconductor layers CoZnO, the electrical spin injection from the magnetic semiconductor CoZnO into the non-magnetic semiconductor ZnO is realized. Based on the measured magnetoresistance and the Schmidt model, the spin polarization ratio in the ZnO semiconductor is deduced to be 11.7% at 90 K and 7.0% at room temperature, respectively.