Low writing energy and sub nanosecond spin torque transfer switching of in-plane magnetic tunnel junction for spin torque transfer random access memory

This work investigated in-plane MgO-based magnetic tunnel junctions (MTJs) for the application of spin torque transfer random access memory (STT-RAM). The MTJ in this work had an resistance area product (RA) 4.3ω μm ², tunneling magnetoresistance ratio ∼135, thermal stability factor δ (H)68 (by field measurement), and δ(I) 50 (by current measurement). The optimal writing energy was found to be 0.286 pJ per bit at 1.54 ns for antiparallel (AP) state to parallel (P) state switching, and 0.706 pJ per bit at 0.68 ns for P state to AP state switching. Ultra fast spin torque transfer (STT) switching was also observed in this sample at 580 ps (AP to P) and 560 ps (P to AP). As a result, 0.6-1.3 GHz was determined to be the optimal writing rate from writing energy consumption of view. These results show that in-plane MgO MTJs are still a viable candidate as the fast memory cell for STT-RAM.