Time resolved transport studies of magnetization reversal in orthogonal spin transfer magnetic tunnel junction devices

In this work we report on time resolved magnetization reversal driven by spin transfer torque in an orthogonal spin transfer (OST) magnetic tunnel junction device. We focus on the transitions from parallel (P) to antiparallel (AP) states and the reverse transitions (AP to P) under the influence of 10 ns voltage pulses. The electrical response is monitored with a fast real-time oscilloscope and thus timing information of the reversal process is obtained. The P to AP transition switching time decreases with increasing current and shows only direct switching behavior. The AP to P transition shows similar behavior, but has a broader distribution of switching times at high currents. The rare AP to P switching events that occur at later times are due to the occurrence of a pre-oscillation, which could be identified in time resolve voltage traces. A possible origin of these pre-oscillations is seen in micromagnetic simulations, where they are associated with the breakdown of the uniform precession of the magnetization, and lead to reversal of the magnetization at later times.