# Effect of laser induced orbital momentum on magnetization switching

## TL;DR

This paper critically examines the role of laser-induced orbital momentum in magnetization switching, finding it insufficient for single-pulse reversal and proposing a domain expansion mechanism requiring multiple pulses.

## Contribution

It provides a quantitative analysis of the orbital momentum induced by circularly polarized ultrafast laser pulses, challenging previous assumptions about its sufficiency for magnetization reversal.

## Key findings

- Induced orbital momentum is too small for single-pulse magnetization reversal.
- Magnetization reversal likely occurs via domain expansion over multiple pulses.
- Single ultrafast laser pulse cannot directly switch magnetization through orbital momentum alone.

## Abstract

The observed magnetization switching by circularly polarized ultrafast laser pulses has been attributed to the inverse Faraday effect in which the induced non-equilibrium orbital momentum serves as an effective magnetic filed via spin-orbit coupling for magnetization rotation and switching. We critically examine this scenario by explicitly calculating the magnitude of the induced orbital momentum for generic itinerant band. We show that the calculated induced angular momentum is not large enough for reversing the magnetization in one laser pulse with the order of 100 femtosecond duration. Instead, we propose that each laser pulse is capable to expand a reverse domain a few nano-meters and it takes multiple pulses to complete the magnetization reversal process via domain wall motion.