Twisting Light, Steering Spins: Gold Nanoparticle Magnetization via Inverse Faraday and Orbital Angular Momentum

Abstract

We present a new approach to controlling magnetization in gold nanoparticles using the Inverse Faraday Effect combined with Laguerre-Gauss beams carrying orbital angular momentum. By tailoring the tilt of isophase planes, we induce drift photocurrents that generate magnetic fields tilted by up to 25{\deg} relative to the beam axis. The magnetic orientation can be reversed by switching polarization chirality or the orbital angular momentum sign, and it can be rotated azimuthally by repositioning the particle, accessing any angle over 2{\pi} steradians. This unprecedented level of control extends all-optical magnetization to three-dimensional orientations, potentially at ultrafast timescales given the near-instantaneous nature of the Inverse Faraday Effect. Our results pave the way for advanced spin-based applications, from triggering spin waves in magnetic materials to designing next-generation magnetic memory and logic devices.