Laser induced ultrafast 3d and 4f spin dynamics in CoDy ferrimagnetic alloys as a function of temperature

TL;DR

This study investigates how femtosecond laser pulses affect the ultrafast spin dynamics of 3d and 4f electrons in a CoDy ferrimagnetic alloy across different temperatures, revealing temperature-dependent demagnetization behaviors.

Contribution

It provides the first element- and time-resolved analysis of laser-induced ultrafast spin dynamics in CoDy alloys as a function of temperature, confirming theoretical predictions about critical slowing down.

Findings

Co3d demagnetization time increases near Curie temperature

Dy4f demagnetization time decreases near Curie temperature

Critical slowing down regime vanishes for Dy sublattice

Abstract

We report on an element- and time-resolved investigation of femtosecond laser induced ultrafast dynamics of 3d and 4f spins in a ferrimagnetic Co80Dy20 alloy as a function of temperature. We observe an increase of the Co3d characteristic demagnetization time and a decrease of the Dy4f demagnetization time when the temperature is approaching the Curie temperature. It suggests that the critical slowing down regime, which affects the laser induced ultrafast dynamics in pure 3d transition metals and 4f rare-earth ferromagnetic layers, vanishes for the Dy sublattice in the CoDy alloy, in line with the theoretical predictions of the Landau-Lifshitz-Bloch model.