Structural and magnetic variations of ZnFe_2O_4 spinels-neutron powder diffraction studies

摘要

Variations of the structural and magnetic properties of three chemically identical but differently treated ZnFe_2O_4 compounds have been studied by neutron powder diffraction. The three ZnFe_2O_4 sampls comprise two compacted speciments -(1) annealed and slowly cooled and (2) annealed and quenched-and (3) nanocrystalline material. Unit cells and oxygen positions of teir cubic spinel-type structure as well as inversion parameters x defining the occupations of tetrahedrally and octahedrally coordinated cation sites have been refined. Distinct magnetic properties of the three specimens are related to the degree of inversion: (1) antiferromagnetic log range order below 10.5 K, (2) absence of any long range order, (3) onset of ferromagnetic ordering at 500K.