A Monte Carlo study of the anisotropy effects on the spin state evolution in ultrathin helimagnetnanorings

¹ Institute for Advanced Materials, South China Normal University - Guangzhou 510006, China
² Laboratory of Solid State Microstructures, Nanjing University - Nanjing 210093, China

^(a) xingsengao@scnu.edu.cn
^(b) liujm@nju.edu.cn

Received: 23 September 2014
Accepted: 16 December 2014

Abstract

In this work, the magnetic states in ultrathin helimagnet nanorings were investigated using a Monte Carlo simulation, based on a Heisenberg model involving the short-range exchange coupling, Dzyaloshinsky-Moriya interaction, long-range dipolar interaction, and perpendicular anisotropy. The competition of these interactions leads to the stabilization of various spin states at zero magnetic field, e.g. necklace-like skyrmion chain state, twin-vortex with two coaxial vortices carrying two opposite charities, depending on geometric and anisotropy parameters. A vortex–to–skyrmion-chain transformation triggered by varying the anisotropy was also revealed. Nanorings with different anisotropy also exhibit completely different magnetization reversal hysteresis loop against magnetic field. Finally, a spin state diagram based on anisotropy and magnetic field was constructed. The present work suggests a novel opportunity to manipulate the spin configurations in nanomagnets, which may find applications in high-density data storage or spintronic devices.