Electronic mechanism of sub-100-fs demagnetization induced by a femtosecond light pulse

TL;DR

This study provides a theoretical explanation for ultrafast, sub-100-fs light-induced demagnetization in magnetic materials, emphasizing electronic excitation and redistribution as key mechanisms.

Contribution

It predicts that electronic processes alone can cause rapid demagnetization, advancing understanding of ultrafast magnetic control without phonon or exchange contributions.

Findings

Demagnetization occurs within 100 femtoseconds across various photon energies.

Electronic excitation and redistribution are primary drivers of ultrafast demagnetization.

Phonon and inter-site exchange processes are negligible at these timescales.

Abstract

A quantitative understanding of the processes that trigger light-induced demagnetization on ultrashort timescales is crucial for achieving an ultrafast, radiation-controlled magnetic response in materials. This milestone is essential for developing next-generation magnetic storage devices and ultrafast magnetic switches. In this theoretical study, we investigated demagnetization triggered in a single magnetic domain by light pulses ranging from a few to a few tens of femtoseconds in duration, with photon energies spanning the optical and X-ray regimes, under strongly non-equilibrium conditions. We predicted a loss of magnetization in the sub-100-fs range in all cases, primarily due to the excitation of the electronic system and the subsequent redistribution of electrons within the magneto-sensitive band. The considered timescales were too short for phonon-mediated processes or inter-site Heisenberg exchange processes to contribute significantly. These findings pave the way for highly accurate, radiation-driven magnetization control in magnetic materials at sub-100-femtosecond timescales with potential practical applications.