EPR investigation of substitution position for Fe3+ in LiNbO3:Fe3+ system

The substitution position of the Fe3+ ion in lithium niobate is a disputed and interesting problem. In the present work, by diagonalizing the complete energy matrices for a d5 configuration ion in a trigonal ligand-field and considering the second-order, fourth-order EPR parameters D and (a-F) simultaneously, the substitution position of Fe3+ ion in LiNbO3:Fe3+ system and the local lattice structure around impurity Fe3+ ion have been studied. Our results indicate that the EPR parameters D and (a-F) all show good agreement with those obtained from experiments, whether the Fe3+ is at Li+ or Nb5+ site, by means of the double-displacement model.