Three-fold Symmetry Effect on Mn2+ Centers in a LiNbO3 Crystal

Spin Hamiltonian for the paramagnetic center with a threefold symmetry and high spin (S >= 2) multiplicity should contain the fourth order zerofield splitting (ZFS) terms. Electron magnetic resonance transition lines of the center with S=5/2 are expected to split in a pair when the magnetic field is applied off the principal axes of ZFS, while they are superimposed when the magnetic field is applied parallel to the principal axes of ZFS. In this study we report that the transition lines of Mn2+ centers at the threefold symmetric sites in LiNbO3, chemically equivalent but physically different, split in two due to the nonzero fourth order ZFS term.