Two series of iron-containing solid solutions Bi 2 Mg 1− x Fe x Nb 2 O 9+δ and Bi 2 MgNb 2−2 x Fe 2 x O 9−δ of pyrochlore structure were obtained by the traditional solid phase synthesis method. The electronic state and character of exchange interactions of iron atoms in solid solutions were investigated by methods of magnetic dilution and NEXAFS-spectroscopy. According to X-ray spectroscopy and magnetic susceptibility data, iron(III) atoms are distributed mainly in octahedral positions of niobium(V) and in a dominant amount are in the charge state of Fe(III) in the form of monomers and exchange-bonded clusters mainly with antiferromagnetic type of exchange. Differences in magnetic behavior of iron-containing solid solutions of both series have been revealed. Antiferromagnetic and ferromagnetic exchange can be realized between iron atoms, which, with increasing concentration of paramagnetic atoms and averaging structure distortions, becomes less significant. The parameters of exchange interactions in clusters and distribution of iron paramagnetic atoms depending on the concentration of solid solutions have been calculated.

中文翻译：

---

掺铁多组分铌酸铋铋烧绿石的磁行为

通过传统的固相合成方法，得到了烧绿石结构的两个系列的含铁固溶体Bi 2 Mg 1-x Fe x Nb 2 O 9 +δ和Bi 2 MgNb 2-2 x Fe 2 x O9-δ。通过磁稀释和NEXAFS光谱法研究了固溶态铁原子的电子状态和交换相互作用的特性。根据X射线光谱学和磁化率数据，铁（III）原子主要分布在铌（V）的八面体位置，并且主要以单体形式存在于Fe（III）的电荷状态，并交换-键团簇主要具有反铁磁类型的交换。揭示了两个系列的含铁固溶体在磁性方面的差异。铁原子之间可以实现反铁磁和铁磁交换，随着顺磁性原子浓度的增加和平均结构变形的增加，其重要性降低。计算了簇中交换相互作用的参数和顺磁性铁原子的分布，这取决于固溶体的浓度。