ESR study of rare-earth ions with the effective spin of 1/2 in LiNbO3 crystals

Abstract

Rare-earth ions of Nd3+ and Er3+ in nearly stoichiometric and MgO-doped LiNbO3 crystals, respectively, have been investigated by employing an X-band electron spin resonance (ESR) spectrometer. The grown crystal was heated in Li-rich powder at 1100°C in order to make it nearly stoichiometric by the vapor transport equilibrium technique. Due to the fact that the ESR linewidth is much narrower in the stoichiometric crystal than in the congruent LiNbO3, we were able to determine the hyperfine constants of143Nd and145Nd at 4 K. By codoping MgO into LiNbO3, a new Er3+ center has been observed with a differentg-tensor. We propose that the new Er3+ center in Mg-doped LiNbO3 occupies the niobium site due to the local excessive Mg2+ ion at the lithium site, whereas Nd3+ and Er3+ in congruent crystals reside at the lithium site. The proposal is consistent with theg-value anisotropy.