First principles study of structure and properties of La- and Mn-modified BiFeO₃

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• 作者：V. Antonov ; I. Georgieva ; N. Trendafilova ; D. Kovacheva ; K. Krezhov
• 关键词：Modified multiferroic BiFeO3 ; First principles calculations ; Magnetoelectric ; Optical properties
• 刊名：Solid State Sciences
• 出版年：2012
• 出版时间：July, 2012
• 年：2012
• 卷：14
• 期：7
• 页码：782-788
• 全文大小：1252 K

文摘

First principles calculations have been performed to study the effects of the La³⁺ and Mn³⁺ substitutions in the multiferroic BiFeO₃. The real compositions Bi_1?xLa_xFeO₃ and BiFe_1?xMn_xO₃ with x = 0.0, 0.1, 0.2, 0.3 were modeled by substitution of one, two and three Bi³⁺ or Fe³⁺ by La³⁺ or Mn³⁺ in the orthorhombic BiFeO₃ structure, respectively. Density functional theory within the generalized gradient approximation with Hubbard correction of Dudarev (GGA + U) and plane wave pseudo-potential approach has been used to track the changes that occur in the structural parameters, electronic structure, magnetic, optical and polarization properties of the modified BiFeO₃. The substitution of one Bi³⁺ with La³⁺ increases the band gap energy whereas the augmentation of La³⁺ substitutes decreases it. The substitutions of Fe³⁺ with Mn³⁺ do not change the band gap energy. The calculations predicted larger polarization of the modified BiFeO₃, antiferromagnetism for Bi_1?xLa_xFeO₃ and small ferrimagnetism for BiFe_1?xMn_xO₃. Better multiferroic properties are expected for BiFe_1?xMn_xO₃ materials (x = 0.1, 0.2) due to the increasing polarization and ferrimagnetic behavior. The optical properties were estimated by the calculated imaginary and real parts of the dielectric function. The increase of La³⁺ and Mn³⁺ substitutes lead to lower absorption intensity at energy range 2-7 eV.