Exchange interactions and the state of iron atoms in Bi{sub 3}Nb{sub 1−x}Fe{sub x}O{sub 7−δ}

• Published in: Journal of solid state chemistry Vol. 247
• Main Authors: Chezhina, N.V., Korolev, D.A., Zhuk, N.A., Lutoev, V.P., Makeev, B.A.
• Format: Journal Article
• Language: English
• Published: United States 15.03.2017
• Subjects: BISMUTH COMPOUNDS; DIMERS; ELECTRON SPIN RESONANCE; EXCHANGE INTERACTIONS; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; IRON; IRON COMPOUNDS; MAGNETIC SUSCEPTIBILITY; NIOBIUM COMPOUNDS; OXIDES; PHASE TRANSFORMATIONS; SOLID SOLUTIONS
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/J.JSSC.2016.12.019

On the basis of the results of magnetic susceptibility and ESR studies of the Bi{sub 3}Nb{sub 1−x}Fe{sub x}O{sub 7−δ} solid solutions iron atoms in the solid solutions of cubic modification of bismuth niobate were found to exist as Fe(III) monomers and exchange bound Fe(III)-O-Fe(III) dimers with antiferro- and ferromagnetic type of superexchange. The exchange parameters and the distribution of monomers and dimers in the solid solutions were calculated as a function of paramagnetic atom content. - Graphical abstract: The study of the Bi{sub 3}Nb{sub 1−x}Fe{sub x}O{sub 7−δ} solid solutions showed that the introduction of iron atoms into the structure of Bi{sub 3}NbO{sub 7} stabilizes the cubic structure of bismuth niobate making the phase transition tetragonal ↔ cubic structure irreversible. In the Bi{sub 3}Nb{sub 1−x}Fe{sub x}O{sub 7−δ} solid solutions we observe the formation of dimers with antiferro- and ferromagnetic exchange. Such clusters are partially retained even at the infinite dilution of the solid solution, which testifies for their rigidity. A sufficiently high parameter of ferromagnetic exchange in a dimer (+53 cm{sup −1}) seems to result from iron atoms being located in the vicinity of oxygen vacancy. - Highlights: • The reversible transition cubic – tetragonal modifications in Bi{sub 3}NbO{sub 7} becomes irreversible. • Only cubic modification of Bi{sub 3}Nb{sub 1-x}Fe{sub x}O{sub 7-δ} is stable due to clusters of Fe atoms. • These clusters are sufficiently strong and retained even at the infinite dilution. • The calculations of magnetic susceptibility give the distribution of the clusters and single atoms.