Plasmon-enhanced optical control of magnetism at the nanoscale via the inverse Faraday effect

TL;DR

This paper demonstrates that circularly polarized femtosecond laser pulses can generate local magnetic fields via plasmonic nanostructures, enabling ultrafast, nanoscale control of magnetism with minimal heating effects.

Contribution

It introduces a novel method for local optical control of magnetism at the nanoscale using plasmonic gold nanodiscs and femtosecond laser pulses, advancing spintronics technology.

Findings

Local magnetic fields are generated by exciting gold nanodiscs with circularly polarized femtosecond laser pulses.

Maximum magnetic field strength occurs at wavelengths above the plasmonic resonance, reducing heating.

This approach enables ultrafast, nanoscale manipulation of magnetization in magnetic films.

Abstract

The relationship between magnetization and light has been the subject of intensive research for the past century, focusing on the impact of magnetic moments on light polarization. Conversely, the manipulation of magnetism through polarized light is being investigated to achieve all-optical control of magnetism in spintronics. While remarkable discoveries such as single pulse all-optical switching of the magnetization in thin films and sub-micrometer structures have been reported, the demonstration of local optical control of magnetism at the nanoscale has remained elusive. Here, we show that exciting gold nanodiscs with circularly polarized femtosecond laser pulses leads to the generation of sizeable local magnetic fields that enable ultrafast local control of the magnetization of an adjacent magnetic film. In addition, we find that the highest magnetic fields are generated when exciting the sample at a wavelength larger than that of the actual plasmonic resonance of the gold nanodiscs, so avoiding undesired heating effects due to absorption. Our study paves the way for light-driven control in nanoscale spintronic devices and provides important insights into the generation of magnetic fields in plasmonic nanostructures.