Reversible magnetism switching in graphene-based systems via the decoration of photochromic molecules

By first principles calculations, we demonstrate that when decorated with photochromic molecules, it is possible to use light to reversibly control the magnetic properties of a nanoscale magnetic system. The combination of a graphene-based magnetic system and a photochromic azobenzene molecule is chosen as a model system. The {\it trans} and {\it cis} isomers of the azobenzene molecule that can be converted between each other by means of photoexcitations are found to have drastically different effects on the magnetic properties of the system. The results may pave the way for the future design of light controllable molecular-scale spintronic devices.