Structural and magnetic transitions in the Chevrel-phase compound FeMo6S8

Moessbauer-effect studies and susceptibility measurements have been carried out to characterize the magnetic and structural properties of the Chevrel-phase compound FeMo6S8. The Moessbauer spectra indicate that a structural phase transition occurs at T0approx. =100 K from an ordered form at low temperature to a disordered form of the material at high temperature, accompanied by a hardening of Fe vibrational modes. Susceptibility measurements give average magnetic moments of 1.61μ/sub B//Fe atom and 1.42μ/sub B//Fe atom in the regions below and above T0, respectively. An antiferromagnetic transition is observed at a temperature T/sub N/approx. =41 K. Moessbauer spectra obtained below T/sub N/ show a distribution of magnetic hyperfine fields which are attributed to Fe atoms being distributed among the crystallographically equivalent sites in the low-temperature structure