High spin-filter efficiency in a Co ferrite fabricated by a thermal oxidation

Takahashi, Y. K.; Kasai, S.; Furubayashi, T.; Mitani, S.; Inomata, K.; Hono, K.
February 2010
Applied Physics Letters;2/15/2010, Vol. 96 Issue 7, p072512
Academic Journal
Co ferrites fabricated by a thermal oxidation have been tested as a spin filter. Spin-filter efficiencies of 44% and 4.3% were confirmed at 10 K and RT, respectively, using a magnetic tunnel junction of Pt/CoFe2O4/MgO/Co. By increasing the bias voltage, the tunneling magnetoresistance (TMR) at 10 K increases then decreases. This is interpreted as a tunneling via spin-down conduction band in the Co ferrite. Since the electron at RT is attributed to a hopping conduction on the defect states in the Co ferrite, the reduction of the defects will be the key to achieving a higher spin-filter effect.


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