Temperature dependence of Moessbauer effect in garnet-like iron molybdate

Moessbauer effect on 57Fe nuclei in iron molybdate Fe2(MoO4)3 with garnet structure was investigated in the temperature range 78-873 deg K. The isomeric displacement value at room temperature delta = 0.675+ -0.007 mm/c is in the region which is specific for Fe+3 ions in the octahedron garnet sublattice. The temperature dependence of the isomeric displacement is mainly associated with the temperature dependence of relativistic displacement. The variation of Fe2(MoO4)3 spectrum width is correlated with the assumption on quadrupole mechanism of hyperfine disintegration. At the temperature T=773+-1 K a jump decreasing of the absorption line width is observed indicating to the structural transformation of Fe2(MoO4)3. Isomeric displacement behaviour and probabilities of the effect in the region of the assumed phase transition do not indicate any anomaly. Probability values of the effect in Fe-molybdate at room temperature f=0.47+-0.04 and the characteristics Debye temperature H=250 deg K are smaller than the corresponding parameters for iron ions in the octahedron points of ordinary garnets which may be explained by the ''defective'' crystal structure of Fe2(MoO4)3