Determination of a cation distribution model of the spinel system Fe3−xAlxO4

Mössbauer spectra of several samples of the spinel system Fe3−xAlxO4 with 0 ≦ x ≦ 1.5 were obtained at room temperature and analysed. For x < 0.9 the spectra of the samples show several Zeeman patterns, which are attributed to tetrahedral and octahedral iron cations. With x > 0.9, the spectra show no theoretical Zeeman patterns at room temperature, and a detailed analysis of the spectra measured at 77 and 298 K, and several temperatures above room temperature (up to 647 K) and in a transverse external magnetic field (13 kOe), allows to identify them as relaxation spectra. A cation distribution model is assumed which is able to explain the measured intensity ratios IB/IA after correction of the blackness distortion. Besides a charge density oscillation model is used to explain the structure of the B-site line which is due to the effective charge of the Al3 + ion in the octahedral (B) sublattice.