Dynamics of ferromagnetic bimerons driven by spin currents and magnetic fields

TL;DR

This paper investigates the dynamics of ferromagnetic bimerons driven by spin currents and magnetic fields, revealing their potential for data encoding and control in spintronic devices through analytical and numerical methods.

Contribution

It provides the first combined analytical and numerical analysis of ferromagnetic bimeron dynamics driven by spin currents and magnetic fields, including creation, motion, and suppression of transverse drift.

Findings

Bimerons with opposite topological numbers can be created simultaneously via spin torques.

The speed of bimeron motion driven by spin currents is analytically derived and matches simulations.

Magnetic field gradients and alternating fields influence bimeron propagation and suppress the skyrmion Hall effect.

Abstract

Magnetic bimeron composed of two merons is a topological counterpart of magnetic skyrmion in in-plane magnets, which can be used as the nonvolatile information carrier in spintronic devices. Here we analytically and numerically study the dynamics of ferromagnetic bimerons driven by spin currents and magnetic fields. Numerical simulations demonstrate that two bimerons with opposite signs of topological numbers can be created simultaneously in a ferromagnetic thin film via current-induced spin torques. The current-induced spin torques can also drive the bimeron and its speed is analytically derived, which agrees with the numerical results. Since the bimerons with opposite topological numbers can coexist and have opposite drift directions, two-lane racetracks can be built in order to accurately encode the data bits. In addition, the dynamics of bimerons induced by magnetic field gradients and alternating magnetic fields are investigated. It is found that the bimeron driven by alternating magnetic fields can propagate along a certain direction. Moreover, combining a suitable magnetic field gradient, the Magnus-force-induced transverse motion can be completely suppressed, which implies that there is no skyrmion Hall effect. Our results are useful for understanding of the bimeron dynamics and may provide guidelines for building future bimeron-based spintronic devices.