Periodic magnetic structures generated by spin-polarized currents in nanostripes

TL;DR

This paper numerically investigates how spin-polarized currents induce various stable periodic magnetic structures in ferromagnetic nanostripes, revealing the dependence on stripe width and current saturation behavior.

Contribution

It provides a comprehensive analysis of magnetization patterns in nanostripes under spin-polarized currents, including analytical insights for narrow stripes and identification of multiple stable structures.

Findings

Saturation current varies nonmonotonically with stripe width.

Multiple stable periodic structures are observed below saturation.

Different structures depend on stripe width, from 1D to 2D patterns.

Abstract

The influence of a spin-polarized current on long ferromagnetic nanostripes is studied numerically. The current flows perpendicularly to the stripe. The study is based on the Landau-Lifshitz phenomenological equation with the Slonczewski-Berger spin-torque term. The magnetization behavior is analyzed for all range of the applied currents, up to the saturation. It is shown that the saturation current is a nonmonotonic function of the stripe width. For a stripe width increasing it approaches the saturation value for an infinite film. A number of stable periodic magnetization structures are observed below the saturation. Type of the periodical structure depends on the stripe width. Besides the one-dimensional domain structure, typical for narrow wires, and the two-dimensional vortex-antivortex lattice, typical for wide films, a number of intermediate structures are observed, e.g. cross-tie and diamond state. For narrow stripes an analytical analysis is provided.