中国物理B ›› 2021, Vol. 30 ›› Issue (7): 77503-077503.doi: 10.1088/1674-1056/abf4bc

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Zero-field skyrmions in FeGe thin films stabilized through attaching a perpendicularly magnetized single-domain Ni layer

Zi-Bo Zhang(张子博)1 and Yong Hu(胡勇)1,2,†   

  1. 1 Department of Physics, College of Sciences, Northeastern University, Shenyang 110819, China;
    2 State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819, China
  • 收稿日期:2021-02-27 修回日期:2021-03-23 接受日期:2021-04-05 出版日期:2021-06-22 发布日期:2021-06-24
  • 通讯作者: Yong Hu E-mail:huyong@mail.neu.edu.cn
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant No. 11774045), the Joint Research Fund Liaoning-Shenyang National Laboratory for Materials Science (Grant No. 20180510008), and the Fundamental Research Funds for Central Universities, China (Grant No. N182410008-1).

Zero-field skyrmions in FeGe thin films stabilized through attaching a perpendicularly magnetized single-domain Ni layer

Zi-Bo Zhang(张子博)1 and Yong Hu(胡勇)1,2,†   

  1. 1 Department of Physics, College of Sciences, Northeastern University, Shenyang 110819, China;
    2 State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819, China
  • Received:2021-02-27 Revised:2021-03-23 Accepted:2021-04-05 Online:2021-06-22 Published:2021-06-24
  • Contact: Yong Hu E-mail:huyong@mail.neu.edu.cn
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant No. 11774045), the Joint Research Fund Liaoning-Shenyang National Laboratory for Materials Science (Grant No. 20180510008), and the Fundamental Research Funds for Central Universities, China (Grant No. N182410008-1).

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摘要： A numerical study reports that the zero-field skyrmions in FeGe thin films are stabilized when a FeGe layer is exchange coupled to a single-domain Ni layer, which has been magnetized perpendicularly. Due to the small thickness, an easy-plane anisotropy in the FeGe layer is taken into account, and the skyrmion-crystal state is favored to appear for low anisotropies and intermediate FeGe/Ni interlayer exchange couplings, and finally transformed from a labyrinth-like and into an out-of-plane uniform state for the large couplings or into an in-plane state for the high anisotropies. Furthermore, the maximum skyrmion charge number is bigger for the periodic and fixed boundary conditions with an out-of-plane magnetization; on the contrary, the Bloch-type skyrmions can be frozen and stabilized for the larger couplings on the fixed boundary with an in-plane magnetization, similar to the experimental results of the magnetic-field-induced skyrmions. Finally, the skyrmion charge number and diameter both decrease if the nonmagnetic defects exist, and the skyrmion centers are prone to being captured by defect sites. This work evidences that the ensembles of homochiral skyrmions stabilized in the multilayers fabricated by well-established technologies present a roadmap to design new classes of the materials that can host skyrmions.

关键词: FeGe thin film, zero-field skyrmion, interlayer exchange coupling, Monte Carlo simulation

Abstract: A numerical study reports that the zero-field skyrmions in FeGe thin films are stabilized when a FeGe layer is exchange coupled to a single-domain Ni layer, which has been magnetized perpendicularly. Due to the small thickness, an easy-plane anisotropy in the FeGe layer is taken into account, and the skyrmion-crystal state is favored to appear for low anisotropies and intermediate FeGe/Ni interlayer exchange couplings, and finally transformed from a labyrinth-like and into an out-of-plane uniform state for the large couplings or into an in-plane state for the high anisotropies. Furthermore, the maximum skyrmion charge number is bigger for the periodic and fixed boundary conditions with an out-of-plane magnetization; on the contrary, the Bloch-type skyrmions can be frozen and stabilized for the larger couplings on the fixed boundary with an in-plane magnetization, similar to the experimental results of the magnetic-field-induced skyrmions. Finally, the skyrmion charge number and diameter both decrease if the nonmagnetic defects exist, and the skyrmion centers are prone to being captured by defect sites. This work evidences that the ensembles of homochiral skyrmions stabilized in the multilayers fabricated by well-established technologies present a roadmap to design new classes of the materials that can host skyrmions.

Key words: FeGe thin film, zero-field skyrmion, interlayer exchange coupling, Monte Carlo simulation

中图分类号:  (Magnetic properties of monolayers and thin films)

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75.10.Hk (Classical spin models) 75.40.Mg (Numerical simulation studies)