Effect of Interlayer Coupling of Synthetic Ferrimagnetic Free Layer on Current Induced Magnetization Switching in MTJs

In order to study the effect of the interlayer exchange coupling of synthetic ferrimagnetic (SyF)-free layer on the current induced magnetization switching (CIMS) in magnetic tunnel junctions (MTJs), in the thermal activation regime, we examine the magnetization dynamics of MTJs with the SyF-free layer based on a macrospin model, combining with the STT analysis. Compared with the MTJ with a single layer, the reduction of the critical current (J_c) is observed in the MTJ with the SyF-free layer. The considerable reduction of J_c is also observed in MTJs with the ferromagnetically coupled-free layer over that with the antiferromagnetically coupled free layer. In connection with CIMS in each SyF-free layer of the MTJ, we found two different types of CIMS dependent on J_ex, that is, decoupled CIMS and coupled CIMS.