Optical control of magnetization in a room-temperature magnet: V-Cr Prussian blue analog

We report reversible photoinduced magnetic phenomena for a V-Cr Prussian blue analog (T(c) similar to 350 K). This molecule-based magnet exhibits a decrease in magnetization upon illumination with UV light (lambda similar to 350 nm) and reaches a metastable state that has a long lifetime at low temperatures (>10(6) s at 10 K). This photoexcited magnetic state totally recovers back to the ground state by warming above 250 K, and partially recovers with green light (lambda similar to 514 nm) illumination. The effect of green light is triggered only when the sample is previously UV irradiated, suggesting a hidden metastable magnetic state. The photoinduced magnetic effects are proposed to originate from structural distortion that alters the magnetic exchange coupling and/or anisotropy.