We present the experimental results of current-induced magnetization random switching of MgO-based magnetic tunnel junctions (MTJs) with elliptical-shaped cell of dimension 178 X 133 nm~2. The R-H loop measurements show that the offset field acting on the free layer is oblique, and magnetoresistance change contains both reversible and irreversible portions. The spin-transfer effect was measured with pulsed current of width 10 ms under bias field along easy-axis direction. For bias field equal to or slightly larger than the easy-axis offset field, the MTJ shows random oscillation between the high and low resistance states; however, as the field increases further, a typical R-I hysteresis loop is obtained. The phenomenon may be related to the residue hard-axis offset field.
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