Magnetization switching in the inertial regime

TL;DR

This study numerically compares standard and inertial Landau-Lifshitz-Gilbert equations to analyze ultrafast magnetization switching in thin films, revealing inertial effects extend ballistic switching regions and introduce a resonant energy absorption channel.

Contribution

It demonstrates the impact of inertial effects on magnetization switching dynamics, highlighting differences in energy channels and switching regions compared to standard models.

Findings

Inertial dynamics widen the ballistic switching region by 25%.

An extra kinetic energy channel enables resonant absorption at THz frequencies.

Both equations show similar qualitative switching behavior, with notable quantitative differences.

Abstract

We have numerically solved the Landau-Lifshitz-Gilbert (LLG) equation in its standard and inertial forms to study the magnetization switching dynamics in a $3d$ thin film ferromagnet. The dynamics is triggered by ultrashort magnetic field pulses of varying width and amplitude in the picosecond and Tesla range. We have compared the solutions of the two equations in terms of switching characteristic, speed and energy analysis. Both equations return qualitatively similar switching dynamics, characterized by regions of slower precessional behavior and faster ballistic motion. In case of inertial dynamics, ballistic switching is found in a 25 % wider region in the parameter space given by the magnetic field amplitude and width. The energy analysis of the dynamics is qualitatively different for the standard and inertial LLG equations. In the latter case, an extra energy channel, interpreted as the kinetic energy of the system, is available. Such extra channel is responsible for a resonant energy absorption at THz frequencies, consistent with the occurence of spin nutation.