First-Principles Investigation of Structural, Electronic, and Magnetic Properties of BiFeO3 and Bi2Fe4O9 Nanostructures.

The structural, electronic, and magnetic properties of bismuth ferrite (BiFeO3) and Bi2Fe4O9 nanostructures were investigated using Density Functional Theory (DFT) within the Generalized Gradient Approximation (PBE-GGA) plus U approach. The PBE-GGA + U calculations predict band gaps of 2.4 eV for BiFeO3 and 2.3 eV for Bi2Fe4O9, closely aligning with experimental data. The analysis of partial and total density of states reveals strong hybridization between iron 3d and oxygen 2p states, with a significant contribution from Fe 3d orbitals in both structures. Additionally, nanostructure and crystal symmetry are crucial in influencing the magnetic properties of BiFeO3 and Bi2Fe4O9. Our calculations indicate that the antiferromagnetic phase is energetically more favorable than the ferromagnetic phase in both materials.