Modeling ultrafast demagnetization and spin transport: the interplay of spin-polarized electrons and thermal magnons

Abstract

We theoretically investigate laser-induced spin transport in metallic magnetic heterostructures using an effective spin transport description that treats itinerant electrons and thermal magnons on an equal footing. Electron-magnon scattering is included and taken as the driving force for ultrafast demagnetization. We assume that in the low-fluence limit the magnon system remains in a quasi-equilibrium, allowing a transient nonzero magnon chemical potential. In combination with the diffusive transport equations for the itinerant electrons, the description is used to chart the full spin dynamics within the heterostructure. In agreement with recent experiments, we find that in case the spin-current-receiving material includes an efficient spin dissipation channel, the interfacial spin current becomes directly proportional to the temporal derivative of the magnetization. Based on an analytical calculation, we discuss that other relations between the spin current and magnetization may arise in case the spin-current-receiving material displays inefficient spin-flip scattering. Finally, we discuss the role of (interfacial) magnon transport and show that, a priori, it cannot be neglected. However, its significance strongly depends on the system parameters.

References in corpus (8)

• Spin Seebeck insulator
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• Theory of magnon-driven spin Seebeck effect
• Ultrafast demagnetization in the sp-d model: a theoretical study
• Ultrafast spin-currents and charge conversion at 3d-5d interfaces probed by time-domain terahertz spectroscopy
• Dynamic phase diagram of dc-pumped magnon condensates
• Driving ferromagnets into a critical region of a magnetic phase diagram
• $s$-$d$ model for local and nonlocal spin dynamics in laser-excited magnetic heterostructures

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• Spin-polarized hot electron transport versus spin pumping mediated by local heating
• Nonequilibrium magnons from hot electrons in antiferromagnetic systems
• Ultrafast electron dynamics in Au/Fe/MgO(001) analyzed by Au- and Fe-selective pumping in time-resolved two-photon photoemission spectroscopy: Separation of excitations in adjacent metallic layers
• Ultrafast electron dynamics in altermagnetic materials
• Exploring terahertz-scale exchange resonances in synthetic ferrimagnets with ultrashort optically induced spin currents
• Ultrafast Spin Accumulations Drive Magnetization Reversal in Multilayers
• Interplay of electron-magnon scattering and spin-orbit induced electronic spin-flip scattering in a two-band Stoner model