Evidence from infrared spectra for the magnetic moment directions of CR cations in the spinel ferrites

Infrared spectra of samples of the (A)[B]2O4 spinel ferrites MFe2O4 (M=Fe, Co, Ni, Cu, Cr) were investigated. It was found that the wave number (ν2) corresponding to B–O–B bond vibrations increases with decreasing magnetic moments (μm2) of the M2+ cations, where the magnetic moment of Cr2+ cation is assumed to be antiparallel to the other cations. This assumption is derived from a magnetic ordering model for spinel ferrites proposed recently by our group.