EPR theoretical study of local lattice structure in YAG:Mn2+ system

By diagonalizing a set of complete energy matrices constructed for a d5 configuration ion in a trigonal ligand field, a reasonable interpretation is obtained for the EPR zero-field splitting of Mn2+ ions located at octahedral sites in yttrium aluminum garnet. It is shown that the local lattice structure around an octahedrally coordinated Mn2+ center has an expansion distortion, which may be attributed to the fact that the radius of Mn2+ ion is larger than that of Al3+ ion, and the Mn2+ ion will push the oxygen ligands outwards. Simultaneously, the local lattice structure distortion parameters ΔR=0.1825–0.2158 A and Δθ=1.220°–1.315° for the octahedral Mn2+ center in the crystal are determined, respectively. Meanwhile, we also demonstrated that the empirical impurity–ligand distance R≈RH+12(ri-rh) is not suitable for the YAG:Mn2+ system which has been approximately taken in previous works.