Theoretical Conditions for Field-Free Magnetization Switching Induced by Spin-Orbit Torque and Dzyaloshinskii–Moriya Interaction

It has been demonstrated recently that field-free switching can be achieved by combining spin-orbit torque (SOT) and Dzyaloshinskii-Moriya interaction (DMI). However, this mechanism only occurs under certain conditions, which have not been well discussed. In this letter, we show that the ratio of the domain wall (DW) width to the nanodot diameter can be utilized as a criterion for determining these conditions. We have studied the influence of different magnetic parameters, such as the exchange constant, magnetic anisotropy, and the DMI magnitude. In addition, we have demonstrated the importance of decreasing the surface energy of the magnetic DW to allow the existence of metastable states. Our work provides guidelines for experiments on DMI-induced field-free magnetization switching, and it also offers a new approach to the design of SOT-based memory or logic circuits.