First principles study on the electronic and magnetic properties in Zn doped BiFe_0.9375Mg_0.0625O₃ with intrinsic defects

Based on first principles spin-polarized density functional theory plus U calculations, the electronic structure and magnetic properties of BiFe_0.9375Mg_0.0625O₃ (BFMO) and Zn doped BiFe_0.9375Mg_0.0625O₃ (BFMZO) are investigated. Compared with the BFMO, the magnetism of BFMZO is greatly enhanced and the calculated net magnetic moment of the supercell is 10.08 μ _B. The improved magnetic moment originates from the destroyed antiferromagnetic spin ordering of Fe³⁺–O–Fe³⁺ and the spin-polarized of O atoms. Electronic and magnetism of BFMZO with intrinsic defects (Bi and O vacancy) are also investigated. The existence of Bi vacancy favors the excitation of the Bi-6 s and O-2p impurity states into the band gap, in contrast, these in-gap impurities are passivated completely with the appearance of O vacancy in BFMZO. The defect of Bi vacancy imposes significant influence on the electronic structure and magnetic behaviors, inducing a reduced net magnetic moment of about 7.98 μ _B, while the O vacancy almost has no effect on the magnetism of BMFZO. The improved ferromagnetism of Zn and Mg codoping suggesting a potential way to enhance the multiferroic properties of BiFeO₃. (paper)