Electron-phonon mediated spin-flip as driving mechanism for ultrafast magnetization dynamics in 3$d$ ferromagnets

TL;DR

This paper demonstrates that electron-phonon mediated spin-flip processes are the primary mechanism driving ultrafast demagnetization in nickel, iron, and cobalt, supported by first-principles calculations and experimental data comparison.

Contribution

It introduces a microscopic three temperature model with parameters from first-principles to explain ultrafast magnetization dynamics in 3d ferromagnets, emphasizing the role of electron-phonon mediated spin-flip.

Findings

Electron-phonon mediated spin-flip drives ultrafast demagnetization.

Small spin-flip probabilities are sufficient for rapid demagnetization.

Model aligns well with experimental magnetization dynamics across different materials.

Abstract

Despite intense experimental effort, theoretical proposals and modeling approaches, a lack of consensus exists about the intrinsic mechanisms driving ultrafast magnetization dynamics in 3$d$ ferromagnets. In this work, we find evidence of electron-phonon mediated spin-flip as the driving mechanism for the ultrafast magnetization dynamics in all three 3$d$ ferromagnets; nickel, iron and cobalt. We use a microscopic three temperature model with parameters calculated from first-principles, which has been validated by direct comparison to the electron and lattice dynamics extracted from previous experiments. By direct comparison to the experimentally measured magnetization dynamics for different laser fluence, we determine the spin-flip probability of each material. In contrast to previous findings but in agreement to ab-initio predictions, we find that relatively small values of the spin-flip probability enable ultrafast demagnetization in all three 3$d$ ferromagnets.