Magnetic susceptibility, EPR, NEXAFS and XPS spectra of Fe-doped CaBi2Nb2O9

In order to study the electronic state of Fe atoms and interatomic exchange interactions in solid solutions of Bi2CaNb2−2xFe2xO9−δ with perovskite structure, methods of magnetic dilution, NEXAFS, XPS and EPR spectroscopy were used. Increased values of the magnetic moment of iron atoms in solid solutions compared to pure spin values for Fe(III) are explained by the presence of clusters of Fe(III) atoms predominantly with antiferromagnetic type of exchange. Exchange parameters and cluster distribution in Bi2CaNb2−2xFe2xO9−δ solid solutions depending on the Fe content were calculated according to the Heisenberg–Dirac–van Vleck model. The effect of calcium atoms on the clusterization degree and intensity of Fe interatomic exchange interactions was displayed. XPS spectra of Bi2CaNb2-2xFe2xO9-δ, were identified to enable estimation of the effective charge of the atoms composing it. The analysis of the NEXAFS Fe2p-spectra of iron oxides and the iron-containing solid solutions revealed that Fe atoms were mainly in an oxidation state of +3. EPR spectra of Fe containing solid solution powder show an intense asymmetric line in the low-field part of the spectra at g = 4.27 with weakly manifested shoulder g ∼ 8–10 and a broad component in the g ∼ 2 range with a high-field wing.