New low symmetry centres of Yb3+ impurities in lithium niobate single crystal

The results of optical spectroscopy and electron paramagnetic resonance studies of Yb3+ impurities in congruent LiNbO3 host crystal ([Li]/[Nb] = 0.94) were reported at low temperatures. Fine and hyperfine EPR transitions were observed for different isotopes of Yb3+ ion. The spectra indicate the presence of few magnetically non-equivalent Yb3+ sites in unit cell of the LiNbO3. Mainly ytterbium centers with C1 lowest point symmetry group are detected; axial symmetry centers are not recognized. The values of the components of the g and A tensors are estimated. The temperature dependence of the intensity, peak-to-peak linewidth and g-parameter of the EPR central line (170Yb) suggests the presence of the Yb3+–Yb3+ pairs in lithium niobate host crystal doped with ytterbium.