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

Abstract

We report reversible photoinduced magnetic phenomena for a V-Cr Prussian blue analog $({T}_{c}\ensuremath{\sim}350\text{ }\text{K})$. This molecule-based magnet exhibits a decrease in magnetization upon illumination with UV light $(\ensuremath{\lambda}\ensuremath{\sim}350\text{ }\text{nm})$ and reaches a metastable state that has a long lifetime at low temperatures ($>{10}^{6}\text{ }\text{s}$ 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 $(\ensuremath{\lambda}\ensuremath{\sim}514\text{ }\text{nm})$ 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.