DFT study on the electronic and magnetic properties of the Sr₂FeNbO₆ compound

The Sr₂FeNbO₆ (SFNO) compound is a material with potential applications to be used as an electrode in solid oxide fuel cells, as well as a photocatalyst material for hydrogen generation. However, there is much controversy on the crystal structure related to this compound. Establishing a crystal structure that correctly describes the electronic and magnetic properties presented by this compound is important to understand the origin of its properties. Theoretical DFT calculations were performed on the cubic, tetragonal, and orthorhombic structure based on the generalized gradient approximation (GGA) and the corrected local density of Hubbard approximation (LDA + U). Our results reveal that the orthorhombic and tetragonal structures are suitable models for reproducing an A-type AFM arrangement and an indirect energy band gap for SFNO in agreement with the reported experimental results if U_Fe = 10 and 9 eV are used respectively. Meanwhile, the cubic structure does not reproduce the SFNO properties since this modeled structure exhibits a metallic and ferromagnetic behavior.