Magnetic vortex-antivortex crystals generated by spin-polarized current

TL;DR

This paper investigates the formation of stable vortex-antivortex superlattices in thin ferromagnetic films driven by strong spin-polarized currents, revealing a critical current threshold and a melting transition.

Contribution

It introduces a new mechanism for current-induced periodic vortex-antivortex lattice formation and confirms analytical predictions with micromagnetic simulations.

Findings

Stable square vortex-antivortex superlattices appear below a critical current.

Vortex crystal melting occurs as current decreases further.

Analytical results are validated by micromagnetic simulations.

Abstract

We study vortex pattern formation in thin ferromagnetic films under the action of strong spin-polarized currents. Considering the currents which are polarized along the normal of the film plane, we determine the critical current above which the film goes to a saturated state with all magnetic moments being perpendicular to the film plane. We show that stable square vortex-antivortex superlattices (\emph{vortex crystals}) appears slightly below the critical current. The melting of the vortex crystal occurs with current further decreasing. A mechanism of current-induced periodic vortex-antivortex lattice formation is proposed. Micromagnetic simulations confirm our analytical results with a high accuracy.