Photo-switching of magnetization in iron nanoparticles

We report the theoretical study of the light-induced switching of magnetization in core-shell nanoparticles. The core of the nanoparticle is made of iron (Fe) coated with the shell of azobenzene. Azobenzene is a photochromic material with reversible trans-cis photoisomerization upon irradiation by UV and visible light. The magnetization of nanoparticles can be reversibly switched using specific wavelengths of light. Using an ab initio parameterization of magnetic interactions we performed Monte Carlo simulations of the magnetization of the core-shell nanoparticle as a function of temperature. The results show that Fe nanoparticle magnetization can be switched by at least 50% because of the photoisomerization of azobenzene at room temperature. Ab initio calculations show that the exchange interaction in Fe dimer is ferromagnetic (FM), and shows a strong modification of exchange interaction parameters by 40% because of the trans-cis photoisomerization of azobenzene. An infinite planar Fe monolayer mimicking the surface of nanoparticle shows a strong modification of exchange interaction parameters (up to 50%) in the monolayer due to trans-cis photoisomerization. The local magnetic moments of Fe sheet increase by only 0.5% due to photoisomerization.