An investigation of the EPR zero-field splitting of Fe3+ ions at tetragonal sites in Tl2MgF4 and Tl2ZnF4 crystals

By analyzing the EPR zero-field splitting parameters of Fe3+ located at tetrahedral site in Tl2MgF4 and Tl2ZnF4 crystals, the local lattice structure for Fe3+ doped in Tl2MgF4 and Tl2ZnF4 crystals is theoretically studied by diagonalizing the complete energy matrices for a d5 configuration ion in a tetragonal ligand-field. From the calculation, the local lattice structure parameters R⊥ = 1.8914 Å, R∥ = 1.84699 Å and R⊥ = 1.88229 Å, R∥ = 1.84490 Å for tetragonal Fe3+ center in Tl2MgF4 and Tl2ZnF4 crystals are determined, respectively. This result suggests that the ligand-fluorines on the C4 axis deviate easily in both two crystals, which is consistent with the conclusion drawn by earlier workers.