A new EPR centre of Er3+ in MgO or ZnO co-doped LiNbO3 single crystals

Electron Paramagnetic Resonance (EPR) experiments have been carried out on congruent crystals of LiNbO3 heavily doped with Mg or Zn and co-doped with Er, In addition to the EPR spectrum previously observed in crystals of LiNbO3:Er3+ an erbium spectrum not reported before is detected in samples co-doped with Mg or Zn. The new spectrum has the following g values: g(parallel to) = 4.3 +/- 0.2, g(perpendicular to) = 7.6 +/- 0.3 for the Mg-doped samples and g(parallel to) = 4.26 +/- 0.05, g(perpendicular to) = 7.8 +/- 0.1 for the Zn-doped ones, coinciding within experimental uncertainty. This spectrum is associated to a new Er3+ centre and is compared to additional centres observed for some trivalent transition metal ions (particularly Cr3+) in LiNbO3 heavily doped with Mg or Zn, On these grounds the new centre can be attributed to Er3+ located at the Nb5+ site of LiNbO3. (C) 1999 Elsevier Science Ltd. All rights reserved.