EPR theoretical study of local lattice structure in YAG:Mn 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 is not suitable for the YAG:Mn²⁺ system which has been approximately taken in previous works.