Stability of in-plane and out-of-plane chiral skyrmions in epitaxial MnSi(111)/Si(111) thin films: Surface twists versus easy-plane anisotropy
Stability of in-plane and out-of-plane chiral skyrmions in epitaxial MnSi(111)/Si(111) thin films: Surface twists versus easy-plane anisotropy
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DOI：
10.1103/physrevb.102.174415
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发表时间：
2020-11-09
影响因子：
3.7
通讯作者：
Uzdin, Valery M.
中科院分区：
文献类型：
--
作者：
Leonov, Andrey O.;Tambovtcev, Ivan M.;Uzdin, Valery M.
本文重新讨论了具有易面各向异性的立方螺旋磁薄膜的理论相图，发现其拓扑结构与文献[E. A. Karhu等人，Rev. B 85，094429（2012）]。对于所施加磁场的面内和面外方向，相图表现出广泛的稳定skyrmions区域，这些区域在很宽的各向异性参数范围内重叠。虽然存在的平面外skyrmions是矛盾的，在以前的理论模型，我们证明，额外的表面扭曲导致其稳定性，而温和的易平面各向异性增加面内skyrmions的稳定范围。此外，各向异性和表面扭曲之间的相互作用引起相对于表面倾斜的稳定螺旋状态。由于在大块helimagnets中不存在，这种斜螺旋在薄膜纳米系统的相图中占据了巨大的面积，并作为锥体和螺旋体之间的连接纽带。我们的理论为外延MnSi（111）/Si（111）薄膜中面内和离面skyrmions的实验研究提供了明确的方向。
The revisited theoretical phase diagrams for thin films of cubic helimagnets with the easy-plane anisotropy are shown to have different topology as previously reported [E. A. Karhu et al., Phys. Rev. B 85, 094429 (2012)]. For both in-plane and out-of-plane directions of an applied magnetic field, the phase diagrams exhibit extensive areas of stable skyrmions, which overlap for a wide range of anisotropy parameters. Although the existence of the out-of-plane skyrmions was contradicted within the previous theoretical models, we prove that additional surface twists lead to their stability, while the moderate easy-plane anisotropy increases the stability range of inplane skyrmions. Moreover, the interplay between the anisotropy and the surface twists gives rise to a stable spiral state canted with respect to the surfaces. Being absent in bulk helimagnets, this oblique spiral occupies vast areas at the phase diagrams in thin-film nanosystems and serves as a connecting-link between cones and helicoids. Our theory gives clear directions for renewed experimental studies of in-plane and out-of-plane skyrmions in epitaxial MnSi(111)/Si(111) thin films.