Berlin 2018 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 27: Spin currents and spin torques

MA 27.8: Vortrag

Mittwoch, 14. März 2018, 11:30–11:45, EB 407

Unified relativistic theory of magnetization dynamics with spin-current tensors — •Ritwik Mondal, Marco Berritta, and Peter M. Oppeneer — Department of Physics and Astronomy, Uppsala University, SE-75120 Uppsala, Sweden

Spin currents play a crucial role in operative properties of spintronic devices. To study current-driven magnetization dynamics, spin-torque terms providing the action of spin-polarized currents have previously been added in a phenomenological way to the Landau-Lifshitz-Gilbert (LLG) equation describing the local spin dynamics, yet without derivation from fundamental principles^1,2. Starting from the Dirac-Kohn-Sham theory³ and incorporating nonlocal spin transport we rigorously derive various spin-torque terms that appear in current-driven magnetization dynamics. In particular we obtain an extended magnetization dynamics equation that precisely contains the nonrelativistic adiabatic and relativistic nonadiabatic spin-transfer torques of the form proposed by Berger as well as relativistic spin-orbit torques⁴. We derive in addition a previously unnoticed relativistic spin-torque term and show that the various obtained spin-torque terms do not appear in the same mathematical form in the Landau-Lifshitz and LLG equations of spin dynamics.
¹D. C. Ralph and M. D. Stiles, J. Magn. Magn. Mater. 320, 1190 (2008). ²P. Gambardella and I. M. Miron, Phil. Trans. Roy. Soc. London A 369, 3175 (2011). ³R. Mondal, M. Berritta and P. M. Oppeneer, Phys. Rev. B 94, 144419 (2016). ⁴ S. Zhang and Z. Li, Phys. Rev. Lett. 93, 127204 (2004).