Adaptive Compact Magnetic Tunnel Junction Model

Abstract — Electrical control of magnetic tunnel junc-tions (MTJs) provides opportunities to introduce MTJs into high-performance applications requiring low power consumption. The magnetic state of an MTJ can be electrically controlled through: 1) the spin transfer torque (STT) effect; 2) the voltage controlled magnetic anisotropy (VCMA) effect; and 3) the fusion of STT and VCMA. Several compact models have been published for MTJs. All of these models consider an MTJ whose magnetic state is controlled through the STT effect. In this paper, a model of an MTJ comprising a free layer, an analysis layer, and a spin polarizing layer is described. The MTJ compact model, adaptive compact MTJ (ACM) model, includes the effects of asymmetry on the MTJ behavior, and models a device controlled through the STT, VCMA, or a fused STT–VCMA mechanism. The ACM model includes the dynamics of the junction temperature. The proposed model can be adapted to experimental configurations including in-plane MTJ (IMTJ), IMTJ with a perpendicular-to-the-plane polarizer, perpendicular-to-the-plane MTJ (PMTJ), and PMTJ with an additional easy axis. The ACM model is validated with published experimental data, showing reasonably accurate results with an average error of less than 6%. Index Terms — Compact model, magnetic tunnel junction (MTJ), spin transfer torque (STT), voltage controlled magnetic anisotropy (VCMA). I