Sub-wavelength localized all-optical helicity-independent magnetic switching using plasmonic gold nanostructures

TL;DR

This study demonstrates sub-wavelength localized all-optical helicity-independent magnetic switching using plasmonic gold nanostructures on GdTbCo films, enabling nanoscale magnetic control with ultrafast laser pulses for potential high-density data storage.

Contribution

The paper introduces a novel approach combining plasmonic gold nanostructures with magnetic films to achieve localized AO-HIS at sub-wavelength scales, advancing magnetic data storage technology.

Findings

Localized AO-HIS achieved at 240 nm scale

Single 370 fs laser pulse induces magnetic switching

Plasmonic nanostructures enhance electromagnetic fields for switching

Abstract

All-optical helicity-independent switching (AO-HIS) is of interest for ultrafast and energy efficient magnetic switching in future magnetic data storage approaches. Yet, to achieve high bit density magnetic recording it is necessary to reduce the size of the magnetic bits addressed by laser pulses at well-controlled positions. Metallic nanostructures that support localized surface plasmons enable spatial electromagnetic confinement well below the diffraction limit and rare-earth transition metal alloys such as GdTbCo have demonstrated nanometre-sized stable domains. Here, we deposit plasmonic gold nanostructures on a GdTbCo film and probe the magnetic state using magnetic force microscopy. We observe localized AO-HIS down to a critical dimension of 240 nm after excitation of the gold nanostructures by a single 370 fs long laser pulse with a centre wavelength of 1030 nm. We demonstrate that the strong localization of optical fields through plasmonic nanostructures enables reproducible localized nanoscale AO-HIS at sub-wavelength length scales. We study the influence of the localized electromagnetic field enhancement by the plasmonic nanostructures on the required fluence to switch the magnetization.