Mn²⁺defects in LiNbO₃: an electron nuclear double resonance (ENDOR) investigation of the Mn²⁺site and the local disorder

Abstract

With ENDOR, Mn2+ centres in both stoichiometric and congruent LiNbO3 have been investigated. An analysis of four identified Li shells with 24 Li neighbours gives sufficient proof for the Mn2+ occupying a Li site. In stoichiometric LiNbO3 both neighbouring on-axis Nb nuclei were also identified and found to experience changed electric field gradients compared with remote Nb nuclei and NMR data in the literature. Signs of the parameters of the Mn2+ spin Hamiltonian (A/sub //, perpendicular to /<0, D>O, P>0) have been determined. Most centres probably contain a defect such as charge-compensating Li vacancy in the first Li shell. As inferred from line-broadening effects, additional defects, especially in congruent crystals, have a measurable influence on the relaxation of nuclei near to the Mn2+.

Photorefractive properties of MnO-doped near stoichiometric LiNbO3 crystals

“…Doping with ions of high polarization ability enhances the deformation degree of O 2p orbits, which results in narrowing of the forbidden band and shifting the absorption edge to the red, and vice versa. In the present study, Mn ions replace Li ions and occupy the location of Li ions [8,9]. Mn ions with higher polarization ability than Li ions made the absorption band shift to the red, and the higher the concentration of Mn ions is, the more the absorption edge shifts to the red.…”

The influences of ZnO doping concentration on structure and photorefractive properties of Zn:Fe:LiNbO3 crystals grown by TSSG method

“…Doping with ions of high polarization ability enhances the deformation degree of O 2p orbits, which results in narrowing of the forbidden band and shifting the absorption edge to the red, and vice versa. In the present study, Fe ions replace Li ions and occupy the location of Li ions [7]. Fe ions which have higher polarization ability than Li ions make the absorption edge shift to the red.…”

Substitutional site and defect structure of Ni2+in LiNbO3crystal studied from the optical and electron paramagnetic resonance spectra

“…In fact, not only Ni 2+ ion, but also the other non-pentavalent ions (e.g. Co 2+ [17], Mn 2+ [32], Fe 3+ [33], Ti 4+ [16] and rare earth ions Pr 3+ , Nd 3+ , Eu 3+ , Dy 3+ , Ho 3+ , Er 3+ , Tm 3+ and Yb 3+ [34]) in LiNbO 3 substitute for Li + ions and shift along C 3 axis. Considering that the valence and/or size of impurities are unlike those of the replaced Li + ion, the displacements can be understandable.…”