Abstract
Mossbauer studies of ceramic samples of the antiferromagnetic perovskite PbFe2/3W1/3O3 have been carried out. It has been established that the temperature of transition to the magnetically ordered state is TN = 365 K. Iron ions in PbFe2/3W1/3O3 are found to reside in the high-spin Fe3+ state. The Fe3+ ions occupy inequivalent positions differing in the nearest cation environment, or more precisely, tungsten and iron ions are distributed in a random manner over the sites of the octahedral sublattice. The inequivalent positions arise as a result of the Fe and W ions being statistically distributed over the octahedral sublattice. For T > 0 K, magnetic fields at the nuclei and, hence, the average thermodynamic values of the magnetic moments of Fe3+ ions occupying inequivalent positions are different and, at a given temperature, are determined by the number of the nearest magnetic neighbors, with the effective magnetic fields (Heff) varying differently with temperature. As the temperature is lowered, the fields Heff level off gradually in response to the effective magnetic fields of iron ions having different numbers of exchange bonds leveling off with decreasing temperature which lowers thermal excitation.
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