Ultrafast magnetization reversal in ferromagnetic spin valves: An <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>s</mml:mi><mml:mtext>−</mml:mtext><mml:mi>d</mml:mi></mml:mrow></mml:math> model perspective
Quentin Remy
Abstract
We present an extension to simple $s\text{\ensuremath{-}}d$ models, aiming at simulating ultrafast magnetization dynamics and spin transport in metallic heterostructures. In particular, we consider an alternative spin dissipation channel due to a finite exchange splitting of the $s$ band. From this theory, we show three different mechanisms governing the dynamics of spin accumulation. On top of the already widely discussed ``$\ensuremath{-}dM/dt$'' electron-magnon mechanism, we study the role of a dynamic change of exchange splitting (of conduction electrons) as well as the rotation of spins reflected at an interface with a ferromagnet. Finally, we use the presented theory to explain the recent observation of subpicosecond reversal of a ferromagnet in rare-earth free spin valves. Our conclusion agrees with the one of J. Igarashi et al. [Nat. Mater. (2023)] favoring magnetization reversal due to the rotation of the spin polarization of a reflected spin current.