MOSSBAUER SPECTROSCOPY OF STOICHIOMETRIC AND NON-STOICHIOMETRIC MAGNETITE

X-ray analysis, chemical analysis, magnetic measurements, and room temperature Mössbauer spectra, with and without the presence of a transverse magnetic field of 8.4 kG have been obtained for two samples of magnetite, one nearly stoichiometric and the other highly non-stoichiometric. The crystallographic structure of the non-stoichiometric sample has been found to be identical with that of the stoichiometric sample, and the vacancies located predominantly at the octahedral sites. The magnetic fields at the Fe nuclei in magnetite have been found to be negative and the LambMössbauer factor for octahedral and tetrahedral iron ions have been found to be equal within experimental error. It has been established that the fast electron hopping process, present in magnetite, is essentially a pair-localized phenomenon, that is, limited to available (Fe2+-Fe3+) octahedral pairs, with the non-paired octahedral Fe3+ ions not participating in the hopping process. Significant delocalization of the process appears to occur only in highly stoichiometric samples. © 1969.