Study of EPR spectra for octahedral Fe3+ center in lutetium aluminum garnet

The EPR spectra of octahedral Fe3+ center in lutetium aluminum garnet have been studied by means of the complete energy matrices for a d5 configuration ion in a trigonal ligand-field. It is manifested that the local lattice structure around an octahedrally coordinated Fe3+ center has an expansion distortion from that of undistorted host Al3+ ion. The expansion distortion can be ascribed to the fact that the radius of Fe3+ ion is bigger than that of Al3+ ion, and consequently the Fe3+ ion pushes the oxygen ligands outwards. Simultaneously, for the octahedral Fe3+ center in the crystal, the local lattice structure parameters, R = (2.007 ± 0.022) Å and θ = (52.708 ± 0.032)°, which reflect the interactions between impurity and crystal lattice, are determined from our calculation, and EPR parameters a, D, and (a − F) also get a unified explanation.