Spin-3/2 Iron Ferromagnet: Its Mössbauer and Magnetic Properties

A spin-3/2 ferromagnetic iron compound is reported. The ferromagnet is bis-($N,N$-diethyldithiocarbamato) ironIII chloride, and has a Curie temperature of 2.5^∘{}K. Extensive susceptibility, ESR, and M\"ossbauer data are presented which establish conclusively that the ground electronic state of iron in this system is a spin quartet, S=3/2. This behavior is uncommon for iron, and the present system is apparently the initial instance of a spin-3/2 iron ferromagnet. The iron in this complex is pentacoordinate, with site symmetry C2V, as shown by Hoskins, Martin, and White. A consideration of the ligand field problem associated with this symmetry suggests the origin of the quartet ground term. The effects of relaxation phenomena in the ferromagnetic state have been observed in some of the M\"ossbauer spectra.