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 Co Fe 2 O 4 tunnel barriers via tunneling magnetoresistance (TMR) measurements. Pt ( 111 ) ∕ Co Fe 2 O 4 ( 111 ) ∕ γ - Al 2 O 3 ( 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. Co Fe 2 O 4 tunnel barriers therefore provide a model system to investigate spin filtering in a wide range of temperatures.