Anomalous Optically Induced Nonvolatile Magnetization Effect in Mn3O4 Superparamagnetic Nanoparticles

Compared to the normal memory effect observed in interacting magnetic nanoparticles, here, an anomalous photo-induced magnetization in Mn3O4 superparamagnetic nanoparticles is reported. When the nanoparticles are frozen below blocking temperature, the incident light can create a "melting" of the frozen spins on Mn3O4, leading to a nonvolatile memory effect in magnetization. In addition, the photo-induced magnetization will change to another on/off response as the temperature rise above blocking temperature. Most interestingly, it is found that the immediate change of magnetization when removing off the light is closely related to the phase transition of Mn3O4. The nonvolatile magnetization effect triggered by the significant photo-magnetism coupling is promising for searching next-generation optical-based devices.