Sub-200ps spin transfer torque switching in in-plane magnetic tunnel junctions with interface perpendicular anisotropy

Ultrafast spin transfer torque (STT) switching in an in-plane MgO magnetic tunnel junction with 50nm×150nm elliptical shape was demonstrated in this paper. Switching speeds as short as 165ps and 190ps at 50% and 98% switching probabilities, respectively, were observed without external field assistance in a thermally stable junction with a 101% tunnelling magnetoresistance ratio. The minimum writing energy of P-AP switching for 50% and 98% switching probability are 0.16pJ and 0.21pJ, respectively. The observed ultrafast switching is believed to occur because of partially cancelled out-of-plane demagnetizing field in the free layer from interface perpendicular anisotropy between the MgO layer and the Co ₂₀Fe ₆₀B ₂₀ layer. High J/J _c0 ratio and magnetization nucleation at the edge of free layer, which result from the reduced perpendicular demagnetizing field, are possibly two major factors that contribute to the ultrafast STT switching.