Effect of light on the magnetic properties of cobalt ferrite nanoparticles

We report variations in the coercivity of CoFe2O4 nanoparticles as a function of particle size, temperature and light intensity. For 30 nm particles, this change in was 2300 Oe at 10K, 120 Oe at 170K, for a light intensity of under 2 milliwatts. The remanent magnetization was nearly unchanged by illumination. A simple model of optical absorption followed by electron transfer between Co2+ and Fe3+ ions is proposed.