A Study of the Magnetic Properties of the FeTiO_3-αFe_2O_3 System by Neutron Diffraction and the Mossbauer Effect

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The solid solutions (1-x)FeTiO_3-xFe_2O_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[xFe^<3+>, (1-x)Fe^<2+>] and B[xFe^<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 ferrirnagnetic phases reveals that both sublattice moments, at zero magnetic field, fall considerably short of the theoretical values. In addition, Mossbauer patterns indicate that paramagnetic behavior persists over a rather wide temperature range below the Neel 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 Mossbauer absorption by solid solutions above their Neel points can be interpreted as a superposition of the absorption peaks of Fe^<2+> and Fe^<3+>.
社団法人日本物理学会の論文
1962-10-05