The Role of Concentration, Site, and O Vacancy on Magnetic and Optical Properties of Cu‐Doped Anatase TiO2

Abstract

Cu‐doped TiO2$\left(\text{TiO}\right)_{2}$ is a dilute magnetic semiconductor with excellent electrical, magnetic, and optical properties. Herein, first‐principles methods are employed to investigate its electronic structure, magnetic properties, and optical behavior. The results demonstrate that Cu‐doped TiO2$\left(\text{TiO}\right)_{2}$ exhibits intrinsic ferromagnetism. The presence of O vacancies facilitates the ferromagnetic exchange between Cu ions by forming bound magnetic polarons (BMPs). This finding validates the BMPs model and explains for the decrease in magnetic properties during annealing under O2 conditions. As the concentration of Cu increases, the system undergoes a transition from a semiconductor to a metal. Cu ions exhibit a preference for a compact configuration and display either paramagnetism or antiferromagnetism. The spin polarization can be effectively controlled from 0% to 100% by adjusting the concentration and site of Cu. Additionally, Cu doping leads to a reduction in the bandgap and an extension of the absorption range into the infrared region. The absorption intensity is positively correlated with the concentration. The presence of a spin‐polarized intermediate band indicates a correlation between the spin of the excited electron and the energy of the absorbed photon. Overall, Cu‐doped TiO2$\left(\text{TiO}\right)_{2}$ shows significant potential for applications in spintronics and spin‐related optics, including photospintronics and spin photocatalysis.