Tuning and controlling magnetic states by light is of great interest for applications such as magneto-optical recording and sensing devices. In this research, the change of sign and adjustability of magnetoresistance by light is shown experimentally. In a simple device, a p-n junction is created at the interface of a thin layer of n-type WS2 and p-type Co3O4. The device displays positive magnetoresistance in the dark, while under light illumination, it displays negative magnetoresistance. We suggest that this effect may be due to the suppression of photogenerated electron-hole recombination under the Zeeman effect. The findings of this research can lead to the development of practical fields such as light sensor systems or magnetoresistance memory devices of the new generation.
