Electronic and magnetic properties of metal diiodides MI2 (M=V, Cr, Mn, Fe, Co, Ni, and Cd) from 129I Mössbauer spectroscopy

The hyperfine interaction parameters at the iodine site in various metal diiodides (M=V, Cr, Mn, Fe, Co, Ni, and Cd) were measured using the 27.8 keV Mössbauer transition in 129I. Charge densities in the valence orbitals are deduced from an interpretation of isomer shift and quadrupole coupling constant values. Magnetic hyperfine interactions transferred at the originally diamagnetic iodine ion in the magnetically ordered phases of the compounds allow one to determine the unpaired spin densities in the valence orbitals. Information relative to the magnetic structures is obtained from the number and intensities of magnetically nonequivalent sites and from the relative orientation between the transferred field and the electric field gradient axes. The Mössbauer spectra of 129Xe impurities created by β− decay of 129I in the NiI2 lattice reveal the absence of bonding of xenon atoms in this matrix.