Room temperature spin filtering in epitaxial cobalt-ferrite tunnel barriers

The authors 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)∕γ-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 2K and −3% at 290K. 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.