Scaling Study of Spin-Hall-Assisted Spin Transfer Torque Driven Magnetization Switching in the Presence of Dzyaloshinskii-Moriya Interaction

Spin-hall-assisted spin transfer torque (SHA-STT) can achieve high-speed, magnetic-field-free, and high-reliable magnetization switching in a three-terminal device consisting of magnetic tunnel junctions (MTJ) above a heavy-metal. Nowadays, the development of perpendicular magnetic anisotropy drives the continuous scaling of the MTJ. In addition, an asymmetric exchange interaction called Dzyaloshinskii-Moriya interaction (DMI) inevitably exists at the heavy metal/ferromagnet interface and has a considerable influence on the magnetization dynamics. Considering these factors, in this work, we study the scaling performance of the SHA-STT driven magnetization dynamics in the presence of DMI. Simulation results demonstrate that, for nonzero DMI, the magnetization switching is activated by domain nucleation, whose mechanism is strongly dependent on the MTJ size and DMI magnitude. The critical SHE current density for magnetization switching decreases with the enlarged MTJ or enhanced DMI. In the presence of DMI, the switching time decreases with the scaling of the MTJ. Moreover, compared with the case of zero DMI, the switching speed is improved or deteriorated for the weak or strong DMI, respectively. Our work demonstrates that the MTJ size and DMI magnitude should be optimized in order to achieve a good tradeoff among a set of performance metrics of the SHA-STT devices.