MAGNETIC-STRUCTURE OF NONSTOICHIOMETRIC FERROUS OXIDE

Neutron diffraction experiments have been carried out at room temperature and 4.2K on polycrystalline samples of FezO with z=0.943, 0.938 and 0.929. At room temperature, the ratio of octahedral iron vacancies to tetrahedral iron interstitials is close to 3 and is therefore in agreement with the defect cluster proposed by Catlow and Fender (1975). Examination of the 4.2K data has led to a model for magnetic ordering around the clusters. The interstitial cations and surrounding iron atoms are coupled by an antiferromagnetic exchange interaction. The spins in this region lie in the (111) plane, not along (111) as in the defect-free regions. The number of spins lying in the (111) plane is consistent with Catlow and Fender's model.