Topological textures and their bifurcation processes in 2D ferromagnetic thin films |
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| Institution: | 1. Department of Physics, Shanghai University, Shanghai 200444, PR China;2. Qian Weichang College, Shanghai University, Shanghai 200444, PR China;3. Key Lab for Astrophysics, Shanghai 200234, PR China;4. Shanghai Key Laboratory of High Temperature Superconductors, Shanghai 200444, PR China;1. Institute of Super Microstructure and Ultrafast Process in Advanced Materials, College of Physics and Electronics, Central South University, 605 South Lushan Road, Changsha 410012, PR China;2. Hunan Key Laboratory for Super-microstructure and Ultrafast Process, Central South University, 932 South Lushan Road, Changsha 410012, PR China;3. Department of Physics and Astronomy, University of Rochester, Rochester, NY 14534, USA;1. Mechanical and Aeronautics Engineering Department, University of Patras, 26500 Rio, Patras, Greece;2. Mechanical Engineering Department, Technological Educational Institute of Western Greece, Patras, Greece;3. Mechanical Engineering Department, Central Greece University of Applied Sciences, Chalkis, Greece;1. School of Civil Engineering and Communication, North China University of Water Resources and Electric Power, Zhengzhou 450045, China;2. Hezhou University, Hezhou 542899, China;1. Department of Optics and Spectroscopy, Voronezh State University, Voronezh 394006, Russia;2. B.I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, Minsk 220072, Belarus;3. P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow 119991, Russia |
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| Abstract: | In this paper, by the use of the topological current theory, the topological structures and the dynamic processes in thin-film ferromagnetic systems are investigated directly from the viewpoint of topology. It is found that the topological charge of a thin-film ferromagnetic system can be changed by annihilation or creation processes of opposite polarized vortex–antivortex pairs taking place at space–time singularities of the normalized magnetization vector field of the system, the variation of the topological charge is integer and can further be expressed in terms of the Hopf indices and Brouwer degrees of the magnetization vector field around the singularities. Moreover, the change of the topological charge of the system is crucial to vortex core reversal processes in ferromagnetic thin films. With the help of the topological current theory and implicit function theorem, the processes of vortex merging, splitting as well as vortex core reversal are discussed in detail. |
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| Keywords: | Magnetic vortex Skyrmion Topological current Vortex core Switching Magnetic thin film Topological structure |
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