An attempt to simulate laser-induced all-optical spin switching in a crystalline ferrimagnet

TL;DR

This paper models laser-induced all-optical spin switching in a crystalline ferrimagnet using first-principles calculations and the Heisenberg exchange model, revealing the critical role of exchange interactions in the switching process.

Contribution

It introduces a simulation approach combining first-principles methods with the Heisenberg model to study AOS in Mn$_2$RuGa, highlighting the influence of exchange interactions.

Findings

Optimal laser field amplitude for switching identified

Exchange interaction strength significantly affects switchability

Weakening exchange can prevent spin switching

Abstract

Interest in all-optical spin switching (AOS) is growing rapidly. The recent discovery of AOS in Mn$_2$RuGa provides a much needed clean case of crystalline ferrimagnets for theoretical simulations. Here, we attempt to simulate it using the state-of-the-art first-principles method combined with the Heisenberg exchange model. We first compute the spin moments at two inequivalent manganese sites and then feed them into our model Hamiltonian. We employ an ultrafast laser pulse to switch the spins. We find that there is a similar optimal laser field amplitude to switch spins. However, we find that the exchange interaction has a significant effect on the system switchability. Weakening the exchange interaction could make the system unswitchable. This provides a crucial insight into the switching mechanism in ferrimagnets.