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arXiv · 1912.01736

Spin-orbit torque-mediated spin-wave excitation as an alternative paradigm for femtomagnetism

G. P. Zhang·M. Murakami·Y. H. Bai·Thomas F. George·X. S. Wu
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Abstract

Laser-induced femtosecond demagnetization, femtomagnetism, offers a potential route to develop faster magnetic storage devices. It is generally believed that the traditional spin-wave theory, which is developed for thermally driven slow demagnetization, can not explain this rapid demagnetization by design. Here we show that this traditional spin-wave theory, once augmented by laser-induced spin-orbit torque, provides a highly efficient paradigm for demagnetization, by capturing low-energy spin-wave excitation that is absent in existing mechanisms. Our paradigm is different from existing ones, but does not exclude them. Microscopically, we find that optical spin-orbit torque generates massive spin waves across several hundred lattice sites, collapsing the long-range spin-spin correlation within 20 fs. Our finding does not only explain new experiments, but also establishes an alternative paradigm for femtomagnetism. It is expected to have far-reaching impacts on future research.

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G. P. Zhang, M. Murakami, Y. H. Bai, Thomas F. George, X. S. Wu. 2019-12-03. Spin-orbit torque-mediated spin-wave excitation as an alternative paradigm for femtomagnetism. https://doi.org/10.1063/1.5110522

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