Reduction of the switching speed in current-induced magnetization reversal due to domain states on applying nano-second current pulses

In this paper, it is shown that during the precessional reversal, the magnetic moment can be trapped into a state with many domains, which decrease the switching speed. Pillar-shaped trilayers of composition Co/Cu/Co are utilized to measure the switching speed for the antiparallel (AP) to parallel (P) transition. A slow current ramp is applied to the sample to measure the hysteresis in the resistance to see the effect of the nanosecond pulse. Similar measurements are carried out for measuring the P to AP switching speed. Results show that sometimes no change in the hysteresis loop is observed indicating that the pulse had no effect on the state of the sample. Sometimes the resistance is observed to jump to the value of the P state resistance indicating that the pulse succeeded in reversing the magnetization fully. In some cases, however, the resistance is observed to change to a value intermediate between the resistances of AP and P states. For the P to AP transition, it is found out that the probability of the domain state formation is much larger than in the case of AP to P transition. These results show that switching probability is reduced due to the incoherent precession of the magnetization during reversal in which this precession is more pronounced for the P to AP state transition.