Ultra-Low-Intensity Magneto-Optical and Mechanical Effects in Metal Nanocolloids

TL;DR

This paper explores how metal nanocolloids exhibit significant magneto-optical effects at ultra-low light intensities and magnetic fields, revealing new interactions between light, magnetization, and nanostructures.

Contribution

It provides a theoretical and numerical analysis of magneto-optical effects in metal nanospheres at very low intensities, aligning with experimental data and introducing plasmonic current loops as a new interaction framework.

Findings

Magneto-optical effects occur at magnetic fields below 1 mT and light intensities under 1 W/cm^2.

Plasmonic current loops and vortex flows explain the interaction mechanisms.

Non-magnetic nanocolloids experience significant torque forces due to photo-induced magneto-optical effects.

Abstract

We theoretically and numerically investigate the linear and nonlinear magneto-optical contributions to the refractive index of metal nanospheres. The analysis is in good agreement with the experimental extinction spectra of gold nanocolloid solutions, with threshold magnetic fields less than 1 mT when illuminated with light intensities less than 1 W/cm^2. Plasmonic current loops and vortex power flows provide a new framework for the dynamical interaction between material magnetization, light polarization and nano-surfaces. The photo-induced magneto-optical interaction of non-magnetic metal nanocolloids imparts significant, non-negligible torque forces in nanofluids.