Transport theory for femtosecond laser-induced spin-transfer torques

Abstract

Ultrafast demagnetization of magnetic layers pumped by a femtosecond laser pulse is accompanied by a nonthermal spin-polarized current of hot electrons. These spin currents are studied here theoretically in a spin valve with noncollinear magnetizations. To this end, we introduce an extended model of superdiffusive spin transport that enables to treat noncollinear magnetic configurations, and apply it to the perpendicular spin valve geometry. We show how spin-transfer torques arise due to this mechanism and calculate their action on the magnetization present, as well as how the latter depends on the thicknesses of the layers and other transport parameters. We demonstrate that there exists a certain optimum thickness of the out-of-plane magnetized spin-current polarizer such that the torque acting on the second magnetic layer is maximal. Moreover, we study the magnetization dynamics excited by the superdiffusive spin-transfer torque due to the flow of hot electrons employing the Landau-Lifshitz-Gilbert equation. Thereby we show that a femtosecond laser pulse applied to one magnetic layer can excite small-angle precessions of the magnetization in the second magnetic layer. We compare our calculations with recent experimental results.

References in corpus (8)

• Super-Diffusive Spin-Transport as a Mechanism of Ultrafast Demagnetization
• All-optical control of ferromagnetic thin films and nanostructures
• Non-collinear Magnetoelectronics
• Ultrafast photo-magnetic recording in transparent medium
• Ab Initio Theory of Coherent Laser-Induced Magnetization in Metals
• Nanoscale confinement of ultrafast spin transfer torque exciting non-uniform spin dynamics by femtosecond spin current pulses
• Femtosecond spin current pulses generated by the non-thermal spin-dependent Seebeck effect and interacting with ferromagnets in spin valves
• Absorption and generation of femtosecond laser-pulse excited spin currents in non-collinear magnetic bilayers

Cited by in corpus (11)

• Interface reflectivity of a superdiffusive spin current in ultrafast demagnetization and THz emission
• Probing optical spin-currents using THz spin-waves in noncollinear magnetic bilayers
• High-frequency magnon excitation due to femtosecond spin-transfer torques
• Domain wall dynamics due to femtosecond laser-induced superdiffusive spin transport
• Néel-Vector Switching and THz Spin-Wave Excitation in Mn${}_2$Au due to Femtosecond Spin-Transfer Torques
• Micromagnetic view on ultrafast magnon generation by femtosecond spin current pulses
• Impact of intergrain spin transfer torques due to huge thermal gradients on the performance of heat assisted magnetic recording
• Tailoring femtosecond hot-electron pulses for ultrafast spin manipulation
• Theory of superdiffusive spin transport in noncollinear magnetic multilayers
• Nonequilibrium dynamics in a spin valve with noncollinear magnetization
• Optimizing spin-based terahertz emission from magnetic heterostructures