A Study of the Magnetic Properties of the FeTiO₃-αFe₂O₃ System by Neutron Diffraction and the Mössbauer Effect

Abstract

The solid solutions (1- x )FeTiO 3 - x Fe 2 O 3 exhibit strong ferromagnetic moments in the composition range 0.1< x <0.6. In this region cation ordering is thought to occur such that the Fe 2+ and Ti 4+ ions occupy alternate (111) layers, thus forming sublattices A[ x Fe 3+ , (1- x )Fe 2+ ] and B[ x Fe 3+ , (1- x )Ti 4+ ]. A neutron diffraction study shows that at least 95% of the Ti ions are located on the B layer but that they are not ordered within the layer. The temperature dependence of the magnetic intensities of a number of ferrimagnetic phases reveals that both sublattice moments, at zero magnetic field, fall considerably short of the theoretical values. In addition, Mössbauer patterns indicate that paramagnetic behavior persists over a rather wide temperature range below the Néel temperatures of solid solutions in which x =0.21 and x =0.33. These results are interpreted as a consequence of inhomogeneity in the magnetic structure, due to competing interactions as a result of the Ti ions being disordered within the layer. The center shift and quadrupole splitting for FeTiO 3 were measured over a wide temperature range. using these results, the Mössbauer absorption by solid solutions above their Néel points can be interpreted as a superposition of the absorption peaks of Fe 2+ and Fe 3+ .