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 (Tc~350 K). This molecule-based magnet exhibits a decrease in magnetization upon illumination with UV light (λ~350 nm) and reaches a metastable state that has a long lifetime at low temperatures (>106 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 (λ~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.