TbD2 and HoD2 have the calcium fluoride type of structure and become antiferromagnetic below 40° and 8°K, respectively. A powder neutron diffraction study of TbD2 at 4°K revealed a sinusoidal modulation of basic magnetic ordering of the first kind, in which ferromagnetic (001) layers are coupled antiparallel to the two adjacent layers. Both the magnetic moment and the wave vector are directed along the [001] axis, with a periodicity of about 24 Å. The moment associated with the Tb ion is 7.9 μB. The diffraction pattern observed for HoD2 was quite complicated and attempts to index the magnetic reflections either with multiple cell dimensions or with simple modulation of a few basic antiferromagnetic structures have proved unsuccessful.

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+ .

The magnetic structures of solid solutions (1−x)Cr2O3-xFe2O3 have been determined by neutron diffraction and magnetic measurements. The different antiferromagnetic structures of Cr2O3 and Fe2O3 are revealed to be connected through cone spiral structures in such a way that continuity is preserved. For the purpose of describing the latter, the fundamental Cr2O3 type of magnetic structure is divided into two sublattices, within each of which the spins are coupled ferromagnetically, with antiferromagnetic coupling between the sublattices. The addition of Fe2O3 creates a cone spiral within each sublattice, both the cone axis and the spiral wave vector lying along the hexagonal c-axis. The cone angle increases with increasing Fe2O3 content up to x = 0.15. p ]In the region 0.2 ⩽ x ⩽ 0.35, the cone axis lies perpendicular to the c-axis, although the spiral wave vector remains parallel to the latter, resulting in a cycloidal arrangement. The spin components along the cone axis now have the fundamental Fe2O3 type of magnetic structure. As the Fe2O3 content increases, the cone angle decreases, until finally when this becomes zero, the Fe2O3 type of magnetic structure is attained.