COVALENCY EFFECTS AND THE PRESSURE DEPENDENCE OF THE MOESSBAUER LINE SHIFTS FOR SPINEL-TYPE FERRITES.

In our previous papers we paid attention to the essential role of the oxygen parameter u in the Moessbauer spectroscopy of ferrites with spinel structure. The analysis of the type of the interconnection between the Mossbauer line shifts for Fe**3** plus nuclei in the tetrahedral and octahedral positions and the lattice parameter a within the limits of the molecular orbital method shows that one of the main factors of this complex interconnection is the difference between the values of u for spinel-type ferrites. If we take into account that the external pressure p can lead in fact not only to variation of the lattice parameter a but to a change of the oxygen parameter u as well, then one can get an expression for the change of the shift part connected with covalency effects. This expression is presented and discussed in the note.