Magnetochemical investigation of the layered solid solution KFexTi1 − 2xNb1 + xO5: Evidence of Fe3+ aggregation

The results of a magnetochemical investigation of the solid solution KFexTi1 − 2xNb1 + xO5, isotypic with layered KTiNbO5, are reported. The temperature dependence of the magnetic susceptibility points to a weak antiferromagnetism ( ≈ −3 cm−1); this is consistent with a fully ordered distribution of Fe3+ on one of the two sets of octahedra (OcI), as deduced from the XRD structure determination. Modeling the FeOFe exchange interactions in the diluted compositions (x ≤ 0.075), from the concentration and temperature dependence of the magnetic susceptibility, gives evidence of Fe3+ aggregation phenomena. For the lowest concentrations, such clustering can be described in terms of only dimers. The as-calculated values of the amount of dimers, for example 36% for x = 0.045, are found to be much larger than that corresponding to a random distribution of Fe3+ on the OcI site.