Selection Rules for All-Optical Magnetic Recording in Iron Garnet

TL;DR

This paper experimentally uncovers the polarization and wavelength selection rules enabling all-optical magnetic switching in Co-doped garnet films, highlighting the role of d-electron transitions in spin coupling at room temperature.

Contribution

It identifies specific polarization and wavelength conditions for ultrafast photo-magnetic recording, advancing understanding of laser-induced magnetic switching mechanisms.

Findings

Switching achieved at room temperature within narrow spectral ranges.

Polarization along <110> or <100> axes enables switching.

D-electron transitions in Co-sublattices are key to the effect.

Abstract

Finding an electronic transition a subtle excitation of which can launch dramatic changes of electric, optical or magnetic properties of media is one of the long-standing dreams in the field of photo-induced phase transitions [1-5]. Therefore the discovery of the magnetization switching only by a femtosecond laser pulse [6-10] triggered intense discussions about mechanisms responsible for these laser-induced changes. Here we report the experimentally revealed selection rules on polarization and wavelengths of ultrafast photo-magnetic recording in Co-doped garnet film and identify the workspace of the parameters (magnetic damping, wavelength and polarization of light) allowing this effect. The all-optical magnetic switching under both single pulse and multiple-pulse sequences can be achieved at room temperature, in narrow spectral ranges with light polarized either along <110> or <100> crystallographic axes of the garnet. The revealed selection rules indicate that the excitations responsible for the coupling of light to spins are d-electron transitions in octahedral and tetrahedral Co-sublattices, respectively.