Time: Wednesday, October 24th, 11:40
Speaker: Anatoly ZVEZDIN, Moscow
We study ultrafast spin dynamics and all-optical photo-magnetic switching in transparent magnetic films with an example of the ferromagnetic films with compensation temperature. The corresponding H-T phase diagrams of the GdFeCo , TbFeCo and epitaxial ferrite-garnet films depending on the parameters of the materials were constructed.A possibility of ultrafast non-thermal magnetization switching in garnet films was shown in the recent experimental work [1]. Understanding all-optical switching in magnetic dielectrics is an important step towards realization of ultrafast magnetic memory with record low energy per bit writing.
The theoretical model is based on the nonlinear Landau-Lifshitz-Gilbert equations fora [001] iron garnet film with uniform magnetization.The effect of the femtosecond laser pulse is described as an additional optical spin-torque, which is quadratic in laser electric field. We conducted simulations of the magnetization dynamics after the impact of a single femtosecond linearly polarized laser pulse in cases of different polarizations of the latter: along <100> and <110> directions. As a result, different switching patterns were obtained in agreement with the recent experimental work [1]. By changing the polarization of the laser pulse different outcomes of the magnetization dynamics were studied, which include repeatable magnetization reversal under alternation of different laser pulse polarizations.
The work was supported by RSF grant No. 17-12-01333.
[1] A. Stupakiewicz et al. Nature, 542 (2017), 71–74.