Crystallograhic and magnetic properties of Fe1−xNixGa2O4

We report the crystallographic and magnetic effects on inverse spinel Fe1−xNixGa2O4 (0.0 ≤ x ≤ 0.9) due to doped Ni cations. The crystalline structures of Fe1−xNixGa2O4 (0.0 ≤ x ≤ 0.9) were examined by using a Philips X’Pert diffractometer with a Cu Kα radiation (λ = 1.5406 Å) source and analyzed with the Rietveld refinement method. The crystal structures were found to be inverse spinel with space group Fd-3m. From the Rietveld analysis, with increasing Ni concentration, the ratio of magnetic Fe2+ cations, compared to the total number of Fe2+ cations on A-site (tetrahedron) decreased from 43 to 7%, and that on B-site (octahedron) increased from 57 to 93%. The lattice constants a0, and bond length dGa3+−Fe2+[Ni2+]\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$d_{Ga^{3+}-Fe^{2+}[Ni^{2+}]}$$\end{document} on A-site and B-site decreased linearly with increasing Ni concentration. From the temperature dependence of susceptibility χ in zero-field-cooled and field-cooled magnetization under 400 Oe, with increasing Ni concentration, the sample showed a decrease in the freezing temperature Tf. Mössbauer spectra of all samples at room temperature showed 2-sets (A-site, and B-site) with large electric quadrupole splitting. The Mössbauer absorption area ratio of A-site decreased, while that of B-site increased with increasing Ni concentration, which is accord with the Rietveld refinement analysis of the XRD results.