The effect of magnetic annealing on barrier asymmetry in Co_(40)Fe_(40)B_(20)/MgO magnetic tunnel junctions

摘要

We demonstrate that high-quality magnetic tunnel junctions with Co_(40)Fe_(40)B_(20) electrodes and crystalline MgO barriers, which show a 230% tunneling magnetoresistance ratio at room temperature, can be successfully fabricated by using a target-facing-target sputtering technique and present the results on the change of barrier asymmetry after the annealing at different temperatures. Bias voltage dependence of magnetoresistance ratio for Co_(40)Fe_(40)B_(20)/MgO magnetic tunnel junctions is highly asymmetrical in the as-deposited states and becomes more symmetrical after magnetic annealing. It also exhibits a shift of the tunneling magnetoresistance maximum to a positive bias voltage under the low-temperature annealing.