Exchange interactions and the state of iron atoms in Bi3Nb1−xFexO7−δ

In the Bi3Nb1−xFexO7−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−1) seems to result from iron atoms being located in the vicinity of oxygen vacancy.326