中国物理B ›› 2024, Vol. 33 ›› Issue (1): 16301-16301.doi: 10.1088/1674-1056/acf91d

所属专题: SPECIAL TOPIC — States and new effects in nonequilibrium

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Ab initio nonadiabatic molecular dynamics study on spin—orbit coupling induced spin dynamics in ferromagnetic metals

Wansong Zhu(朱万松)1, Zhenfa Zheng(郑镇法)1, Qijing Zheng(郑奇靖)1,†, and Jin Zhao(赵瑾)1,2,‡   

  1. 1 Department of Physics and ICQD/Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China;
    2 Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
  • 收稿日期:2023-08-05 修回日期:2023-09-08 接受日期:2023-09-13 出版日期:2023-12-13 发布日期:2023-12-13
  • 通讯作者: Qijing Zheng, Jin Zhao E-mail:zqj@ustc.edu.cn;zhaojin@ustc.edu.cn
  • 基金资助:
    J. Z. acknowledges the support of Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB0450101), the National Natural Science Foundation of China (Grant Nos. 12125408 and 11974322), and the Informatization Plan of Chinese Academy of Sciences (Grant No. CAS-WX2021SF-0105). Q. Z. acknowledges the support of the National Natural Science Foundation of China (Grant No. 12174363). Calculations were performed at Hefei Advanced Computing Center, ORISE supercomputing center and Supercomputing Center at USTC.

Ab initio nonadiabatic molecular dynamics study on spin—orbit coupling induced spin dynamics in ferromagnetic metals

Wansong Zhu(朱万松)1, Zhenfa Zheng(郑镇法)1, Qijing Zheng(郑奇靖)1,†, and Jin Zhao(赵瑾)1,2,‡   

  1. 1 Department of Physics and ICQD/Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China;
    2 Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
  • Received:2023-08-05 Revised:2023-09-08 Accepted:2023-09-13 Online:2023-12-13 Published:2023-12-13
  • Contact: Qijing Zheng, Jin Zhao E-mail:zqj@ustc.edu.cn;zhaojin@ustc.edu.cn
  • Supported by:
    J. Z. acknowledges the support of Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB0450101), the National Natural Science Foundation of China (Grant Nos. 12125408 and 11974322), and the Informatization Plan of Chinese Academy of Sciences (Grant No. CAS-WX2021SF-0105). Q. Z. acknowledges the support of the National Natural Science Foundation of China (Grant No. 12174363). Calculations were performed at Hefei Advanced Computing Center, ORISE supercomputing center and Supercomputing Center at USTC.

摘要: Understanding the photoexcitation induced spin dynamics in ferromagnetic metals is important for the design of photo-controlled ultrafast spintronic device. In this work, by the ab initio nonadiabatic molecular dynamics simulation, we have studied the spin dynamics induced by spin—orbit coupling (SOC) in Co and Fe using both spin-diabatic and spin-adiabatic representations. In Co system, it is found that the Fermi surface (EF) is predominantly contributed by the spin-minority states. The SOC induced spin flip will occur for the photo-excited spin-majority electrons as they relax to the EF, and the spin-minority electrons tend to relax to the EF with the same spin through the electron—phonon coupling (EPC). The reduction of spin-majority electrons and the increase of spin-minority electrons lead to demagnetization of Co within 100 fs. By contrast, in Fe system, the EF is dominated by the spin-majority states. In this case, the SOC induced spin flip occurs for the photo-excited spin-minority electrons, which leads to a magnetization enhancement. If we move the EF of Fe to higher energy by 0.6 eV, the EF will be contributed by the spin-minority states and the demagnetization will be observed again. This work provides a new perspective for understanding the SOC induced spin dynamics mechanism in magnetic metal systems.

关键词: nonadiabatic molecular dynamics, spin dynamics, spin—orbit coupling, ferromagnetic metal

Abstract: Understanding the photoexcitation induced spin dynamics in ferromagnetic metals is important for the design of photo-controlled ultrafast spintronic device. In this work, by the ab initio nonadiabatic molecular dynamics simulation, we have studied the spin dynamics induced by spin—orbit coupling (SOC) in Co and Fe using both spin-diabatic and spin-adiabatic representations. In Co system, it is found that the Fermi surface (EF) is predominantly contributed by the spin-minority states. The SOC induced spin flip will occur for the photo-excited spin-majority electrons as they relax to the EF, and the spin-minority electrons tend to relax to the EF with the same spin through the electron—phonon coupling (EPC). The reduction of spin-majority electrons and the increase of spin-minority electrons lead to demagnetization of Co within 100 fs. By contrast, in Fe system, the EF is dominated by the spin-majority states. In this case, the SOC induced spin flip occurs for the photo-excited spin-minority electrons, which leads to a magnetization enhancement. If we move the EF of Fe to higher energy by 0.6 eV, the EF will be contributed by the spin-minority states and the demagnetization will be observed again. This work provides a new perspective for understanding the SOC induced spin dynamics mechanism in magnetic metal systems.

Key words: nonadiabatic molecular dynamics, spin dynamics, spin—orbit coupling, ferromagnetic metal

中图分类号:  (First-principles theory)

  • 63.20.dk
75.70.Tj (Spin-orbit effects) 67.30.hj (Spin dynamics) 63.20.kd (Phonon-electron interactions)