Exchange relaxation as the mechanism of ultrafast spin reorientation in two-sublattice ferrimagnets

TL;DR

This paper presents an exact solution for the ultrafast spin reorientation in two-sublattice ferrimagnets, revealing nonlinear dynamics including spin switching induced by femtosecond laser pulses.

Contribution

It introduces a novel exact solution accounting for exchange relaxation, describing both longitudinal and precessional spin dynamics in ferrimagnets.

Findings

Identifies nonlinear regimes of spin dynamics including spin switching.

Describes the role of exchange relaxation in ultrafast spin reorientation.

Provides a theoretical framework matching experimental observations in GdFeCo.

Abstract

In the exchange approximation, an exact solution is obtained for the sublattice magnetizations evolution in a two-sublattice ferrimagnet. Nonlinear regimes of spin dynamics are found that include both the longitudinal and precessional evolution of the sublattice magnetizations, with the account taken of the exchange relaxation. In particular, those regimes describe the spin switching observed in the GdFeCo alloy under the influence of a femtosecond laser pulse.