Direct evidence of spin filtering across MnFe[subscript 2]O[subscript 4] tunnel barrier by Meservey-Tedrow experiment

A spin filtering effect has been evidenced in epitaxial MnFe[subscript 2]O[subscript 4] tunnel barriers directly by Meservey-Tedrow experiments. The asymmetry of the Zeeman-split tunneling conductance curves of the superconducting Al spin analyzer in Pt(111)/MnFe[subscript 2]O[subscript 4](111)/γ-Al[subscript 2]O[subscript 3](111)/Al tunnel junctions revealed a positive spin-polarization (up to +9%), proving the potential of manganese ferrite for generation of a spin-polarized current. A negatively polarized spin filtering being expected theoretically, different mechanisms are discussed to explain both sign and amplitude of the measured spin-polarization.National Science Foundation (U.S.). Division of Materials Research (Grant 0504158)National Science Foundation (U.S.). Division of Materials Research (Grant 1207469)United States. Office of Naval Research (Grant N00014-09-1-0177)United States. Office of Naval Research (Grant N00014-13-1-0301