Creation and Annihilation of Skyrmions in the Frustrated Magnets with Competing Exchange Interactions

Yong Hu,An Du,Xiaodan Chi,Yan Liu,Xuesi Li

doi:10.1038/s41598-017-16348-8

Yong Hu, An Du + Show 3 more

Open Access

https://doi.org/10.1038/s41598-017-16348-8

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Abstract

In triangular-lattice magnets, the coexistence of third-neighbor antiferromagnetic and nearest-neighbor ferromagnetic exchange interactions can induce rich magnetic phases including noncoplanar skyrmion crystals. Based on Monte Carlo simulation, we studied the dependence of magnetic phase transition on exchange interaction strength. Under the consideration of uniaxial anisotropy and magnetic field both perpendicular to the film plane, a large antiferromagnetic exchange interaction induces a high frustration. When the value of antiferromagnetic exchange interaction is one and a half times larger than the ferromagnetic one, a magnetic phase composed of canting spin stripes, never observed in the chiral magnets, forms. Interestingly, different canting spin stripes along three 120 degree propagation directions may coexist randomly in a magnetic phase, attesting that the canting spin stripes are three-fold degenerate states akin to helices and the multiple state of canting spin stripes is a circular configuration with zero skyrmion charge number. Moreover, skyrmions and antiskyrmions can be observed simultaneously in the configuration at the low temperature nearly close to 0 K, and their configuration and diameter properties are discussed. Finally, the mechanisms of skyrmion creation and annihilation are properly interpreted by comparing exchange and Zeeman energy terms.

Highlights

In the centrosymmetric compounds which have the helimagnetic structures arising from other interactions, such as magnetic frustration
An unbiased Monte Carlo simulation is performed to demonstrate the effect of exchange interactions on the magnetic skyrmion phase transitions, the skyrmion configurations, and the skyrmion creation and annihilation in the triangular-lattice magnetically frustrated films
We focus on the mechanism to create and annihilate the skyrmions in exchange-interaction-driven frustrated magnets, and the exchange and Zeeman energy densities for j′ = j and 2j as functions of magnetic field are shown in Fig. 6a,b, respectively

Summary

Introduction

In the centrosymmetric compounds which have the helimagnetic structures arising from other interactions, such as magnetic frustration. The sign reversal of skyrmion charge number leads to the opposite direction of the topological Magnus force, and the accumulation of skyrmions and antiskyrmions at the opposite edge due to the skyrmion Hall effect, which may be very useful for implementation of logical operations[10,23]. Based on the magnetization distributions (configurations) and the LTEM patterns of the deflected electrons, they redefined the Bloch- and Néel-type skyrmions and antiskyrmions. Whereas the magnetization is counterclockwise-rotated in a spin cycloid for the Néel-type skyrmions, and no intensity modulation is expected in the case of the Néel-type skyrmions viewed by LTEM due to a closed loop made by the deflected electrons. An unbiased Monte Carlo simulation is performed to demonstrate the effect of exchange interactions on the magnetic skyrmion phase transitions, the skyrmion configurations, and the skyrmion creation and annihilation in the triangular-lattice magnetically frustrated films. To unravel the mechanism of skyrmion formation in the simplest frustrated magnets will help us to understand and design more skyrmionic devices based on diverse types of competing interactions

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