Magnetic radial vortex stabilization and efficient manipulation driven by the Dzyaloshinskii Moriya Interaction and the spin-transfer torque

TL;DR

This paper demonstrates how interfacial Dzyaloshinskii Moriya Interaction stabilizes a novel radial vortex state with unique topological properties, enabling efficient manipulation via spin-transfer torque for potential ultralow power memory devices.

Contribution

It introduces the stabilization of a radial vortex with non-integer skyrmion number using i DMI and shows its efficient switching with low current densities.

Findings

i DMI stabilizes radial vortex with non-integer skyrmion number

Radial vortex can be switched with current density below 10^6 A/cm^2

Switching involves vortex nucleation and vortex-antivortex annihilation

Abstract

Solitons are very promising for the design of next generation of ultralow power devices for storage and computation. The key ingredient to achieve this goal is the fundamental understanding of their stabilization and manipulation. Here, we show how the interfacial Dzyaloshinskii Moriya Interaction (i DMI) is able to lift the energy degeneracy of a magnetic vortex state by stabilizing a topological soliton with radial chirality, hereafter called radial vortex. It has a non-integer skyrmion number S (0.5<|S|<1) due to both the vortex core polarity and the magnetization tilting induced by the i DMI boundary conditions. Micromagnetic simulations predict that a magnetoresistive memory based on the radial vortex state in both free and polarizer layers can be efficiently switched by a threshold current density smaller than 106 A/cm2. The switching processes occur via the nucleation of topologically connected vortices and vortex antivortex pairs, followed by spin wave emissions due to vortex antivortex annihilations.