Superexchange coupling in fluorides and fluoro-complexes of elements in the first transition series.

Abstract

Theories of magnetism with special reference to the indirect exchange mechanism and ligand field theory are discussed. The magnetic susceptibilities of VF3, MnF3, NiF 2-MgF2, K2NiF4-K2 MgF4, and K3NiF6-K2.8AlF 5.8 were studied range of 90°K to 300°K. The effective magnetic moments of the paramagnetic ions increases as their concentration in the solid solutions decreases. This is explained as being due to the presence of indirect interactions between paramagnetic ions in the pure substance which are decreased by magnetic dilution. It was found that the moments are still dependent upon temperature even at infinite dilution. This behaviour is ascribed to the orbital contribution which is itself temperature dependent. Evidence is adduced for the presence of Ni (III) ion impurities in the NiF2-MgF2 system when it is contaminated with traces of oxide.