A Mössbauer Effect And Magnetic Study of Fe₂(SO₄)₃ and Fe₂(MoO₄)₃, Two L-Type Ferrimagnets

Abstract

In his 1948 classification^1,2 of magnetic interactions Néel proposed that a material which was basically antiferromagnetic could show ferrimagnetic behavior, perhaps over a limited temperature range, if the moments of the magnetic ions on the antiferromagnetically coupled sublattices were slightly different. He classified this type of magnetic behavior as L-type ferrimagnetism. The different moments on the magnetic ions might arise from inequivalent exchange coupling pathways in the different sublattices. This difference could occur if the magnetic ions, which may be in quite similar chemical environments, are on crystallographically distinct lattice sites. The different moments on the antiferromagnetically coupled sublattices would lead to ferrimagnetism with a spontaneous magnetization and a large susceptibility. If the chemical environments of the crystallographically distinct magnetic ions are quite similar, then the moments should saturate at low temperatures to similar values. At these low temperatures the material would exhibit normal antiferromagnetic behavior. Hence the magnetic susceptibilty would exhibit a field dependent peak at the temperature with the maximum difference in the magnetic moments, and would fall to a low value at low temperature. This type of behavior is shown schematically in Figure 1.