Modeling the diversity of laser-induced spin dynamics in Gd/FeCo multilayers

TL;DR

This paper develops a theoretical model using the Landau-Lifshitz-Bloch equation to explain the diverse laser-induced spin dynamics in Gd/FeCo multilayers, matching experimental observations and exploring the effects of magnetic field and temperature.

Contribution

It introduces a comprehensive theoretical framework that captures both transverse and longitudinal spin dynamics, including ultrafast all-optical switching, in ferrimagnetic multilayers.

Findings

Model describes ultrafast helicity-independent switching

Matches experimental phase diagrams and switching behavior

Highlights exchange relaxation's role in high-fluence switching

Abstract

Recent experimental findings revealed an exceptionally diverse laser-induced spin dynamics tunable by magnetic field ($H$) and temperature ($T$) in ferrimagnetic Gd/FeCo multilayers, however the theoretical picture of these processes remains unclear. To bridge this gap, we theoretically explore $H-T$ phase diagram of such a ferrimagnet and perform a modeling of the laser-induced spin dynamics using the Landau-Lifshitz-Bloch equation. Our model can describe both transverse and longitudinal spin dynamics in the ferrimagnetic multilayer, including ultrafast helicity-independent all-optical switching, observed experimentally. We explore the magnetic $H-T$ phase diagram and the full range of magnetization switching at low laser fluences. We also examine the exchange relaxation mechanism critical for ultrafast switching at higher laser fluences. Our theoretical findings closely match experimental results, demonstrating the validity of the proposed models and their ability to predict static and dynamic magnetic properties of ferrimagnetic multilayers as functions of magnetic field and temperature.