2010 Volume 34 Issue 2 Pages 96-99
A magnetic tunnel junction (MTJ) spin-filter device of Pt/Co ferrite/MgO/Co demonstrated -19.8 % tunnel magnetoresistance (TMR) and 27.5% spin-filter efficiency at 10 K. By increasing the bias voltage, the TMR at 10 K first increased and then decreased, exhibiting a maximum at 0.17 V. This anomalous dependence of TMR on bias was interpreted as tunneling via the spin-down conduction band in the Co ferrite. At room temperature (RT), the tunneling mechanism was thought to originate from hopping in the defect states due to structural and chemical defects in the Co ferrite. To achieve higher spin-filter effect at RT, it is important to reduce the defects in the Co ferrite barrier.
