The study of polycrystalline PbMg1/3Nb2/3O3by 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 centres of rhombic, axial and cubic symmetry in average and individual low-symmetry fluctuations were described by spin Hamiltonians with distributed constants. The other type of centre at T=100 K was found to retain the pure cubic symmetry of ideal homogeneous regions. The superhyperfine interaction between Fe3+ and neighbouring 207Pb nuclei is 4 mT. The mechanisms by which the paramagnetic centre symmetry is decreased involves a contribution from the cation disorder in B sites and a temperature dependent contribution of lattice distortions in polar regions. The oxygen sublattice shift was estimated.