Neutron Diffraction Study of Antiferromagnetic MnTiO₃ and NiTiO₃

MnTiO 3 and NiTiO 3 have a rhombohedral crystal structure similar to FeTiO 3 in which layers of Fe and Ti atoms alternate along the rhombohedral axis with oxygen layers between them. A powder neutron diffraction study shows that MnTiO 3 has a magnetic structure with the Mn 2+ spins antiparallel within each layer. On the other hand, NiTiO 3 has the same magnetic structure as FeTiO 3 , in which the spins are parallel within each layer and adjacent layers are antiparallel. The spins are directed along the [111] direction in MnTiO 3 and perpendicular to it in NiTiO 3 . In addition to the magnetic study, the nuclear intensities indicate that the Ni and Ti in NiTiO 3 are only 88 per cent ordered.