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

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.

21 pages, 5 figures, 2 tables

References in corpus (7)

• Super-Diffusive Spin-Transport as a Mechanism of Ultrafast Demagnetization
• Perspective: Ultrafast magnetism and THz spintronics
• All-optical spin switching: A new frontier in femtomagnetism -- A short review and a simple theory
• Switching ferromagnetic spins by an ultrafast laser pulse: Emergence of giant optical spin-orbit torque
• Magnetization dynamics and damping due to electron-phonon scattering in a ferrimagnetic exchange model
• First-principles and model simulation of all-optical spin reversal
• Distinguishing Local and non-Local Demagnetization in Ferromagnetic FePt Nanoparticles