Influence of annealing on the bias voltage dependence of tunneling magnetoresistance in MgO double-barrier magnetic tunnel junctions with CoFeB electrodes

Double-barrier magnetic tunnel junctions with two MgO barriers and three CoFeB layers exhibiting tunneling magnetoresistance TMR values of more than 100% were fabricated. The bias voltage dependence of the TMR ratio is highly asymmetric after annealing at low temperatures, indicating dissimilar CoFeB/MgO interfaces. The TMR effect decays very slowly for positive bias and is only reduced to half of its maximum value at V1/2=1.88 V when the junctions are processed at 200 °C. The largest output voltage, 0.62 V, is obtained after annealing at 300 °C, a temperature that combines high TMR ratios with a considerable asymmetric bias dependence. © 2006 American Institute of Physics. DOI: 10.1063/1.2362977