Peter M. Oppeneer
Magnetization switching processes in magnetic materials can generally be divided in coherent and incoherent processes. Whereas the latter involve thermal quenching and then rebuilding of the magnetic order, the former are particularly interesting for fast and energy-efficient switching. I will focus on several mechanisms that could provide coherent torques for magnetization switching, in particular, the spin and orbital Hall and Rashba-Edelstein effects and inverse Faraday effect. To understand the possible achievable magnitudes of these mechanisms, we perform ab initio calculations of the current-induced or light-induced magnetizations in selected materials, including ferromagnets and antiferromagnets (AFMs) [1-3].
We show that both the Rashba-Edelstein effect and the inverse Faraday effect can lead to staggered torques in AFM materials [2,3]. Those induced by the inverse Faraday effect are particularly large. For the selected case of AFM CrPt we find, in collaboration with the group of U. Nowak, that coherent ultrafast single-shot switching of the AFM order is possible within less than 200 fs [4]. This is due to the coherent action of the staggered induced moments as well as the speed of exchange enhanced dynamics in AFMs.
[2] L. Salemi et al., Nat. Commun. 10, 5381 (2019)
[3] L. Salemi et al., Phys. Rev. Mater. 5, 074407 (2021)
[4] T. Dannegger et al., Phys. Rev. B 104, L060413 (2021)