$s$-$d$ model for local and nonlocal spin dynamics in laser-excited magnetic heterostructures

Abstract

We discuss a joint microscopic theory for the laser-induced magnetization dynamics and spin transport in magnetic heterostructures based on the $s$-$d$ interaction. Angular momentum transfer is mediated by scattering of itinerant $s$ electrons with the localized ($d$ electron) spins. We use the corresponding rate equations and focus on a spin one-half $d$ electron system, leading to a simplified analytical expression for the dynamics of the local magnetization that is coupled to an equation for the non-equilibrium spin accumulation of the $s$ electrons. We show that this description converges to the microscopic three-temperature model in the limit of a strong $s$-$d$ coupling. The equation for the spin accumulation is used to introduce diffusive spin transport. The presented numerical solutions show that during the laser-induced demagnetization in a ferromagnetic metal a short-lived spin accumulation is created that counteracts the demagnetization process. Moreover, the spin accumulation leads to the generation of a spin current at the interface of a ferromagnetic and non-magnetic metal. Depending on the specific magnetic system, both local spin dissipation and interfacial spin transport are able to enhance the demagnetization rate by providing relaxation channels for the spin accumulation that is build up during demagnetization in the ferromagnetic material.

arXiv commentPublished version

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• Ultrafast demagnetization in ferromagnetic materials: Origins and progress
• Evidence of extreme domain wall speeds under ultrafast optical excitation
• Ultrafast Demagnetization through Femtosecond Generation of Non-thermal Magnons
• Element resolved evidence of superdiffusive terahertz spin current arising from ultrafast demagnetization process
• Ultrafast magnetization reversal in ferromagnetic spin-valves: an s-d model perspective
• Spin-polarized hot electron transport versus spin pumping mediated by local heating
• Different spin relaxation property observed in linearly and circularly polarized laser induced terahertz emission from Bi/Co bilayer
• Ultrafast Spin Accumulations Drive Magnetization Reversal in Multilayers
• Probing Laser-Induced Spin-Current Generation in Synthetic Ferrimagnets Using Spin Waves
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