Realistic micromagnetic description of all-optical ultrafast switching processes in ferrimagnetic alloys

Abstract

Both helicity-independent and helicity-dependent all-optical switching processes driven by single ultrashort laser pulse have been experimentally demonstrated in ferrimagnetic alloys as GdFeCo. Although the switching has been previously reproduced by atomistic simulations, the lack of a robust micromagnetic framework for ferrimagnets limits the predictions to small nano-systems, whereas the experiments are usually performed with lasers and samples of tens of micrometers. Here we develop a micromagnetic model based on the extended Landau-Lifshitz-Bloch equation, which is firstly validated by directly reproducing atomistic results for small samples and uniform laser heating. After that, the model is used to study ultrafast single shot all-optical switching in ferrimagnetic alloys under realistic conditions. We find that the helicity-independent switching under a linearly polarized laser pulse is a pure thermal phenomenon, in which the size of inverted area directly correlates with the maximum electron temperature in the sample. On the other hand, the analysis of the helicity-dependent processes under circular polarized pulses in ferrimagnetic alloys with different composition indicates qualitative differences between the results predicted by the magnetic circular dichroism and the ones from inverse Faraday effect. Based on these predictions, we propose experiments that would allow to resolve the controversy over the physical phenomenon that underlies these helicity-dependent all optical processes.

Nonvolatile Memristive Materials and Physical Modeling for In‐Memory and In‐Sensor Computing

“…[282,283] Understanding the switching in traditional GdFeCo ferrimagnetic alloys, however, is still difficult. [284,285] The ASD simulations are typically utilized to discern experimental results. [286,287] The electron system can be excited by an input stimulus that extends a few femtoseconds on the timescales of the exchange interaction, enabling studies of the underlying physics controlling switching.…”

“…[ 282,283 ] Understanding the switching in traditional GdFeCo ferrimagnetic alloys, however, is still difficult. [ 284,285 ] The ASD simulations are typically utilized to discern experimental results. [ 286,287 ]…”

“…A conventional two sublattice ferrimagnet was used in a temperature step to furnish information about the spatial distribution of sublattice magnetization. [ 285,303 ] In the absence of a temperature step, a stationary nonequilibrium magnon accumulation occurs, corresponding to the derivative of equilibrium magnetization .…”