Atomistic and ab initio DFT modelling of the defect structures in Al³⁺/Cr³⁺-doped and co-doped Y₃Fe₅O₁₂

Widatallah, Hisham M.; Al-Barwani, Muataz S.; Moore, Elaine A. and Elzain, Mohamed E. (2018). Atomistic and ab initio DFT modelling of the defect structures in Al³⁺/Cr³⁺-doped and co-doped Y₃Fe₅O₁₂. Journal of Physics and Chemistry of Solids, 119 pp. 100–106.

DOI: https://doi.org/10.1016/j.jpcs.2018.03.036

Abstract

The defect structures when Y₃Fe₅O₁₂ is doped with either Al³⁺ or Cr³⁺, and evenly co-doped with both, which have been a matter of controversy in the literature, are modelled using atomistic and ab initio DFT methods. When Y₃Fe₅O₁₂ is doped with Al³⁺, the defect reaction energy obtained marginally favors the preferential substitution of Al³⁺ for Fe³⁺ at the tetrahedral sites as opposed to octahedral ones. This is indicative that for Al³⁺-doped samples processed at elevated temperatures, or containing undetected impurities, the substitution of Al³⁺ for octahedral Fe³⁺ is likely. To model the defect structure of the Cr³⁺ -doped Y₃Fe₅O₁₂, it was essential that the Cr³⁺ ions crystal field stabilization energy (CFSE) and the Fe³⁺-O^2-- Cr³⁺ spin-spin coupling derived from the ab initio DFT calculations ,be taken into account. The results show the substitution of the Cr³⁺ ion for an octahedral Fe³⁺ ion to be energetically favorable relative to its substitution for a tetrahedral Fe³⁺ one. It is also shown that the antisite defect, where the Cr³⁺ ion substitutes for Y³⁺ at a dodecahedral site with the expelled Y³⁺ ion substituting for an octahedral Fe³⁺ ion, is possible under certain processing conditions. For the Al³⁺ /Cr³⁺ co-doped Y₃Fe₅O₁₂, the Al³⁺ and Cr³⁺ ions were found to, respectively, substitute for the tetrahedral and octahedral Fe³⁺ ions. The energy values obtained suggest this defect structure to be insensitive to the processing conditions and/or the presence of undetected impurities. The structural and magnetic implications of these defect structures are discussed

Viewing alternatives

Metrics

Item Actions

Export

You can export this page using these formats Digital Object Identifier - DOI

About

• Item ORO ID
• 54035
• Item Type
• Journal Item
• ISSN
• 0022-3697
• Academic Unit or School
• Faculty of Science, Technology, Engineering and Mathematics (STEM) > Life, Health and Chemical Sciences
  Faculty of Science, Technology, Engineering and Mathematics (STEM)
• Research Group
• Smart Materials
  Chemistry and Materials Research Group
• Copyright Holders
• © 2018 Elsevier Ltd.
• Depositing User
• Elaine Moore