Reorientation processes of tilted skyrmion and spiral states in a bulk cubic helimagnet Cu2OSeO3
Reorientation processes of tilted skyrmion and spiral states in a bulk cubic helimagnet Cu2OSeO3
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DOI：
10.3389/fphy.2023.1105784
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发表时间：
2023-02-02
影响因子：
3.1
通讯作者：
Pappas, Catherine
中科院分区：
文献类型：
--
作者：
Leonov, Andrey O.;Pappas, Catherine
本文系统地研究了立方非中心对称铁磁体中磁态的经典Dzyaloshinskii模型中理论上得到的倾斜螺旋态。这种倾斜的螺旋线在立方和交换各向异性的竞争作用下表现出稳定。通过重点研究这些螺旋线的内部结构以及它们在不同各向异性系数长宽比下的场驱动行为，我们能够捕捉到块状立方螺旋线Cu2OSeO_3的实验结果的主要特征，并向这种手性磁体的完整定量模型又迈进了一步。特别地，我们证明了对于强各向异性值(实验上对应于零附近的低温)，锥形螺线和倾斜螺线之间存在角分离，即锥形螺线翻转成倾斜状态，并且立即构成相对于场方向的有限角度。随着各向异性比的减小，两个螺旋态之间的这种转变几乎是连续的，并对应于实验中更高的温度。此外，我们还研究了由竞争各向异性引起的亚稳态Skyrmion晶格的场驱动重取向，这可能是Cu2OSeO_3实验相图上的一些特殊现象的原因。
We present a systematic study of tilted spiral states obtained theoretically within the classical Dzyaloshinskii model for magnetic states in cubic non-centrosymmetric ferromagnets. Such tilted spirals are shown to stabilize under the competing effect of cubic and exchange anisotropies inherent to cubic helimagnets. By focusing on the internal structure of these spirals and their field-driven behaviour for different aspect ratios of the anisotropy coefficients, we are able to capture the main features of the experimental findings in a bulk cubic helimagnet Cu2OSeO3 and to make a step further towards a complete quantitative model of this chiral magnet. In particular, we show that for strong anisotropy values (which experimentally correspond to low temperatures near zero) there exist an angular separation between the conical and tilted spirals, i.e., the conical spiral flips into a tilted state and immediately composes some finite angle with respect to the field direction. As the anisotropy ratio decreases, such a transition between two spiral states becomes almost continuous and corresponds to higher temperatures at the experiments. In addition, we investigate the field-driven reorientation of metastable skyrmion lattices induced by the competing anisotropies, which may be responsible for some peculiarities at the experimental phase diagrams of Cu2OSeO3.