Domain wall dynamics of ferrimagnets induced by spin-current near the angular momentum compensation temperature

TL;DR

This theoretical study explores how spin-current influences domain wall dynamics in ferrimagnets near the angular momentum compensation temperature, revealing maximum mobility and potential gigahertz oscillations.

Contribution

It provides a comprehensive theoretical framework for understanding domain wall behavior in ferrimagnets near the compensation point, including effects of spin-current polarization and Walker breakdown.

Findings

Maximum domain wall mobility near the compensation temperature for in-plane spin polarization

Out-of-plane polarization does not excite domain wall dynamics below Walker breakdown

Potential for gigahertz oscillations of the antiferromagnetic vector at the compensation point

Abstract

We report on a theoretical study of the spin-current excited dynamics of domain walls (DWs) in ferrimagnets in the vicinity of the angular momentum compensation point. Effective Lagrangian and nonlinear dynamic equations are derived for a two-sublattice ferrimagnet taking into account both spin-torques and external magnetic field. The dynamics of the DW before and after the Walker breakdown is calculated for any direction of the spin current polarization. It is shown that for the in-plane polarization of the spin current, the DW mobility reaches a maximum near the temperature of the angular momentum compensation. For the out-of-plane spin polarization, in contrast, a spin current with the densities below the Walker breakdown does not excite the dynamics of the DW. After overcoming the Walker breakdown, the domain wall velocity increases linearly with increasing the current density. In this spin-current polarization configuration the possibility of a gigahertz oscillation dynamics of the quasi-antiferromagnetic vector under the action of a damping-like torque in the angular momentum compensation point is demonstrated. Possible structures for experimental demonstration of the considered effects are discussed.