Room temperature spin filtering in epitaxial cobalt-ferrite tunnel barriers

We report direct experimental evidence of room temperature spin filtering in magnetic tunnel junctions (MTJs) containing CoFe2O4 tunnel barriers via tunneling magnetoresistance (TMR) measurements. Pt(111)/CoFe2O4(111)/gamma-Al2O3(111)/Co(0001) fully epitaxial MTJs were grown in order to obtain a high quality system, capable of functioning at room temperature. Spin polarized transport measurements reveal significant TMR values of -18% at 2 K and -3% at 290 K. In addition, the TMR ratio follows a unique bias voltage dependence that has been theoretically predicted to be the signature of spin filtering in MTJs containing magnetic barriers. CoFe2O4 tunnel barriers therefore provide a model system to investigate spin filtering in a wide range of temperatures.