Electronic structure, magnetism, and optical properties of orthorhombic GdFeO3 from first principles

Abstract

Orthorhombic GdFeO$_3$ has attracted considerable attention in recent years because its magnetic structure is similar to that in the well-known BiFeO$_3$ material. We investigate electronic structure, magnetism, and optical properties of the orthorhombic GdFeO$_3$ in terms of density-functional-theory calculations. The modified Becke-Johnson (mBJ) exchange potential is adopted to improve on the description of the electronic structure. Our calculation show that the G-type antiferromagnetic (G-AFM ordering of Fe spins) phase of orthorhombic GdFeO$_3$ is stable compared to other magnetic phases. The semiconductor gap calculated with mBJ, substantially larger than that with GGA, is in good agreement with recent experimental values. Besides, we also investigate effect of the spin-orbit coupling on the electronic structure, and calculate with mBJ the complex dielectric functions and other optical functions of photon energy. The magnetic exchange interactions are also investigated, which gives a Neel temperature close to experimental observation. For comparison towards supporting our results, we study the electronic structure of rhombohedral (R3c) BiFeO$_3$ with mBJ. These lead to a satisfactory theoretical understanding of the electronic structure, magnetism, and optical properties of orthorhombic GdFeO$_3$ and can help elucidate electronic structures and optical properties of other similar materials.