Current-driven domain wall dynamics in ferrimagnetic Ni-doped Mn4N films : very large domain wall velocities and reversal of motion direction across the magnetic compensation point

TL;DR

This study demonstrates extremely high domain wall velocities and a reversal in motion direction in ferrimagnetic Mn4-xNixN films, achieved by tuning Ni content near the magnetic compensation point, with implications for spintronic devices.

Contribution

It reveals how adjusting Ni content in Mn4-xNixN films enables control over domain wall velocity and direction, advancing understanding of spin-transfer torque effects in ferrimagnets.

Findings

Domain wall velocities up to 3000 m/s near compensation point

Reversal of domain wall motion direction across the compensation point

Enhanced spin-transfer torque due to reduced magnetization and high spin polarization

Abstract

Spin-transfer torque (STT) and spin-orbit torque (SOT) are spintronic phenomena allowing magnetization manipulation using electrical currents. Beyond their fundamental interest, they allow developing new classes of magnetic memories and logic devices, in particular based on domain wall (DW) motion. In this work, we report the study of STT driven DW motion in ferrimagnetic manganese nickel nitride (Mn4-xNixN) films, in which a fine adjustment of the Ni content allows setting the magnetic compensation at room temperature. The reduced magnetization, combined with the large spin polarization of conduction electrons, strongly enhances the STT so that domain wall velocities approaching 3000 m/s can be obtained for Ni compositions close to the compensation point. In addition, a reversal of the domain wall motion direction is observed when the magnetic compensation composition is crossed. This striking feature, related to the change of direction of the spin polarization with respect to that of the net magnetization, is clarified by ab initio band structure calculations.