Electronic, magnetic and optical properties of charge-compensated (Nb, TM = Fe, Cr)-codoped SrTiO₃ from first principles

Abstract

Effect of charge compensation codoping on electronic structure, magnetic and optical absorption of SrNb _x Ti_{1-2 x} Fe _x O₃ ((Nb, Fe)-STO) and SrNb _x Ti_{1-2 x} Cr _x O₃ ((Nb, Cr)-STO) within doping concentration x = 0.0625 were investigated by first-principles calculations. Results show that the charge compensation codoping have a significant influence on magnetic and optical properties of SrTiO₃ (STO). The (Nb, Fe) and (Nb, Cr) substitutional codoping STO are more easily formed due to the reduced defect formation energy with respect to that of Fe-doped STO and Cr-doped STO, respectively. The n-type Nb-doped STO semiconductor becomes a half-metal after Cr/Fe codoping. It is found that the (Nb, Fe)-STO and (Nb, Cr)-STO show significant ferromagnetic behavior, which are attributed to the stronger magnetic coupling between the induced free electrons and 3d spin states of Fe and Cr impurities in these codoped systems. The (Nb, Fe)-STO and (Nb, Cr)-STO display better absorption than that of Nb-doped STO in the visible light region, which could be new promising photocatalytic materials.

KEYWORDS:

• Charge compensation codoping
• electronic structure
• ferromagnetic
• optical absorption

Funding

The author is grateful to the National Science Foundation of China for finacial support under Grant #51474011, and the Postdoctoral Science Foundation of China Grant #2014M550337, and the Key Technologies R&D Program of Anhui Province of China Grant #1604a0802122.