磁斯格明子的拓扑保护、纳米尺寸大小且驱动电流密度低的特性，使得其成为下一代自旋电子学存储或逻辑器件的理想信息载体，如赛道存储器、可重构逻辑门、人工神经元器件和用于量子计算的超高密度和低能耗的量子比特。新近发现二维（2D）长程磁序的磁体中可实现各项同性的Néel型斯格明子，如Mn(XY), Cr(X,Y) 以及WTe2/Fe3GeTe2等。然而，具有各向异性的拓扑手性磁结构还没有在二维磁体中得到证实。
Fig. 1 Crystal structure of MCuX2 monolayer, where M and X represent 3d TM and group VIA elements, respectively.
来自中国科学院宁波材料科学与工程技术研究所的杨洪新研究员团队，基于第一性原理计算和原子级微磁学模拟，证实了各向异性的铁磁斯格明子、双半子和反铁磁反斯格明子、双半子可在层状单层范德瓦尔斯磁体MCuX2(M: 3d过渡金属(TM)，X: 第六主族)中实现。此外，该研究还揭示了在连续的应力和温度变化下，单层VCuSe2的磁参数和手性磁结构的尺寸也将发生明显的改变，而且这种反磁斯格明子可以稳定在数百开尔文。该研究对于未来范德瓦尔斯材料和自旋电子学器件的研究具有重要价值。该文近期以博士生尕永龙为第一作者发布于npj Computational Materials 8: 128 (2022)。手机阅读原文，请点击本文底部左下角“阅读原文”，进入后亦可下载全文PDF文件。
Fig.2 The calculated anisotropic DMI of monolayer MCuX2
2D ternary compounds: Anti-topological spin textures
Anti-topological spin textures are realized in two-dimensional ternary compounds protected by D2d crystal symmetry. Due to topological property, nano size and low drive current density of magnetic skyrmions make it an ideal information carrier for the next generation of spintronic storage or logic devices, such as orbital memory, reconfigurable logic gates, artificial neural devices for quantum computing with ultra-high density and low energy consumption of quantum bits. Recent work has revealed the realization of isotropic DMI Nl-type magnetic skyrmion, such as Cr(I,X)3, CrN and WTe2/Fe3GeTe2, in two-dimensional magnets with long range magnetic orderings. However, topological chiral magnetic structures with anisotropic DMI have not been reported in two-dimensional magnets.
Fig.3 Spin configurations of ground states of monolayers MCuX2 in real-space.
A team led by Prof. Hongxin Yang team From Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, via using first-principles calculations and atomistic spin model simulations confirm the anisotropic ferromagnetic (FM) skyrmions, FM bimerons, antiferromagnetic (AFM) skyrmions and AFM bimerons can be realized in layered van der Waals magnet MCuX2 (M: 3D Transition Metal (TM), X: VIA). In addition, it is revealed that the magnetic parameters and the size of the chiral magnetic structures of monolayers VCuSe2 are sensitive to stress and temperature, and the the possibility of antiskyrmions formation up to a hundred Kelvin is demonstrated. This study has important research prospects for the future research of van der Waals magnets and spintronics devices. This paper was recently published in npj Computational Materials 8:128 (2022).
Fig.4 Spin textures for VCuSe2 in real-space.
Anisotropic Dzyaloshinskii-Moriya interaction protected by D2d crystal symmetry in 2D ternary compound (二维三元化合物中发现D2d对称保护的各向异性Dzyaloshinskii-Moriya相互作用)
Yonglong Ga, Qirui Cui, Yingmei Zhu, Dongxing Yu, Liming Wang, Jinghua Liang & Hongxin Yang
Abstract Magnetic skyrmions, topologically protected chiral spin swirling quasiparticles, have attracted great attention in fundamental physics and applications. Recently, the discovery of two-dimensional (2D) van der Waals (vdW) magnets have aroused great interest due to their appealing physical properties. Moreover, both experimental and theoretical works have revealed that isotropic Dzyaloshinskii–Moriya interaction (DMI) can be achieved in 2D magnets or ferromagnet-based heterostructures. However, 2D magnets with anisotropic DMI haven’t been reported yet. Here, via using first-principles calculations, we unveil that anisotropic DMI protected by D2d crystal symmetry can exist in 2D ternary compounds MCuX2 (M: 3d transition metal (TM), X: group VIA). Interestingly, by using micromagnetic simulations, we demonstrate that ferromagnetic (FM) antiskyrmions, FM bimerons, antiferromagnetic (AFM) antiskyrmions, and AFM bimerons can be realized in the MCuX2 family. Our discovery opens up an avenue to creating antiskyrmions and bimerons with anisotropic DMI protected by D2d crystal symmetry in 2D magnets.
Fig. 5 Spin textures for VCuSe2 in real-space.
摘要 磁斯格明子作为一种具有拓扑保护的手性自旋螺旋准粒子，在基础物理和应用中都引起了广泛的关注。近年来，二维(2D)范德华磁体(vdW)的发现由于其诱人的物理特性引起了人们的极大兴趣。此外，实验和理论工作都揭示了二维磁体或铁磁体基异质结构中可以实现各向同性Dzyaloshinskii-Moriya相互作用(DMI)。然而，具有各向异性DMI的二维磁体却罕有报道。本文通过第一性原理计算，揭示了二维三元化合物MCuX2 (M: 3d过渡金属(TM)，X: VIA族)中存在受D2d晶体对称性保护的各向异性DMI。有趣的是，通过微磁模拟，我们证明了在MCuX2家族中可以实现铁磁(FM)反磁斯格明子、FM双半子、反铁磁(AFM)反磁斯格明子和AFM双半子。我们的发现为创造具有各向异性DMI的反磁斯格明子和双半子开辟了一条途径，这些DMI在二维磁体中受到D2d晶体对称性的保护。
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