Domain wall diode based on functionally graded Dzyaloshinskii–Moriya interaction

Abstract

We present a general approach for studying the dynamics of domain walls in biaxial ferromagnetic stripes with functionally graded Dzyaloshinskii–Moriya interaction (DMI). By engineering the spatial profile of the DMI parameter, we propose the concept of a diode, which implements the filtering of domain walls of a certain topological charge and helicity. We base our study on the phenomenological Landau–Lifshitz–Gilbert equations with additional Zhang–Li spin-transfer terms using a collective variable approach. In the effective equations of motion, the gradients of DMI play the role of a driving force, which competes with the current driving. All analytical predictions are confirmed by numerical simulations.