Source: https://lettersonmaterials.com/en/Readers/Article.aspx?aid=1396
Timestamp: 2019-04-20 10:10:46+00:00

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Most bismuth compounds with layered perovskite-like structure, analogs of Aurivillius phases, exhibit ferroelectric properties and are of interest from both practical and theoretical points of view. In this study, we carried out magnetochemical measurements of an electronic state and exchange interactions between iron atoms in the solid solutions Bi5Nb3O15, obtained by heterovalent substitution of niobium by atoms of iron (III). The iron-containing solid solutions were obtained in a narrow concentration range at x≤0.06. The iron-containing solid solutions at concentrations x> 0.005 are characterized by monoclinic distortion of the tetragonal cell (P2/m). The measurements of magnetic susceptibility of the solid solutions were carried out by the Faraday method in the temperature range of 77 - 400 K. The isotherms of a paramagnetic component of magnetic susceptibility of iron atoms are typical of antiferromagnets. The effective magnetic moment of single iron atoms increases with increasing temperature from 6.87 mB (90 K) to 6.92 mB (320 K). The study of the iron-containing Bi5Nb3O15 solid solutions has shown that, in the solid solutions iron (III) atoms aggregate to form dimers and tetramers with antiferromagnetic and ferromagnetic types of exchange. The values of antiferromagnetic and ferromagnetic exchange in dimers, Jdim = - 60 cm-1 and Jdim = 40 cm-1, and tetramers, Jtetr = - 40 cm-1 and Jtetr = 25 cm-1 correspondently.
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