Room-temperature spin filtering in a CoFe2O4/MgAl2O4/Fe3O4 magnetic tunnel barrier

By growing ultrathin and high quality CoFe2O4/MgAl2O4/Fe3O4 epitaxial multilayers, we have demonstrated a room temperature spin filter junction, which could open the way for highly polarized spin injection, single-qubit spintronic measurements, magnetic field sensing, and other applications. In these devices the Fe3O4 layer functions as a source of spin polarized electrons while the CoFe2O4/MgAl2O4 double barrier functions as a spin filter. The current-voltage curves depend on the relative orientation of the magnetization of the Fe3O4 and CoFe2O4 layers and display a large magnetoresistive effect. The inferred net spin polarizations produced by the junctions typically exceeded 70%.