The Temperature Dependent Cation Distribution in Titanomagnetites

A theoretical treatment of the distribution of cations between tetrahedral and octahedral sites is given for titanomagnetites. The theory is based on that of Néel (1950) and involves thermal activation of iron ions whose net preference energy is such that Fe3+ ions prefer tetrahedral sites. The equilibrium cation distribution is derived as a function of temperature and the resulting variation of magnetic moment with composition is shown to be in agreement with the experimental data of previous workers. Further results on single crystals are presented which differ from those previously published. This is interpreted as being due to the different thermal history of the samples in accordance with the theory.