Frequency generation by a magnetic vortex-antivortex dipole in spin-polarized current

TL;DR

This paper investigates the rotational dynamics and frequency generation of a vortex-antivortex dipole in a magnetic element driven by spin-polarized current, combining analytical and numerical methods.

Contribution

It provides a detailed analysis of vortex-antivortex dipole motion under spin-torque, revealing the stabilizing effects and frequency dependence on system parameters.

Findings

Vortex-antivortex dipole exhibits steady rotational motion.

Rotation frequency depends on vortex interaction and external magnetic field.

Spin-torque stabilizes the dipole at a specific separation.

Abstract

A vortex-antivortex (VA) dipole may be generated due to a spin-polarized current flowing through a nano-aperture in a magnetic element. We study the vortex dipole dynamics using the Landau-Lifshitz equation in the presence of an in-plane applied magnetic field and a Slonczewski spin-torque term with in-plane polarization. We establish that the vortex dipole is set in steady state rotational motion. The frequency of rotation is due to two independent forces: the interaction between the two vortices and the external magnetic field. The nonzero skyrmion number of the dipole is responsible for both forces giving rise to rotational dynamics. The spin-torque acts to stabilize the vortex dipole motion at a definite vortex-antivortex separation distance. We give analytical and numerical results for the angular frequency of rotation and VA dipole features as functions of the parameters.