THE STUDY OF POLYCRYSTALLINE PBMG1 3NB2/3O3 BY THE ELECTRON-PARAMAGNETIC-RESONANCE OF FE3+ IONS/

EPR spectra of PMN ceramics doped with 0.1 mol% Fe2O3 were recorded at T = 100 K and T = 475 K and were attributed to Fe3+ ions in positions with different local symmetries. Three types of Fe3+ paramagnetic cen tres of rhombic, axial and cubic symmetry in average and individual lo w-symmetry fluctuations were described by spin Hamiltonians with distr ibuted constants. The other type of centre at T = 100 K was found to r etain the pure cubic symmetry of ideal homogeneous regions. The superh yperfine interaction between Fe3+ and neighbouring Pb-207 nuclei is 4 mT. The mechanisms by which the paramagnetic centre symmetry is decrea sed involves a contribution from the cation disorder in B sites and a temperature-dependent contribution of lattice distortions in polar reg ions. The oxygen sublattice shift was estimated.