Cr³⁺ centres in LiNbO3: Experimental and theoretical investigation of spin hamiltonian parameters

Authors:

• T.H. Yeom,
• Y.M. Chang,
• Czesław Zygmunt Rudowicz,
• S.H. Choh

Abstract

X-band EPR spectra of Cr³⁺ ions in ferroelectric LiNbO₃ single crystal at room temperature are analyzed assuming Cr³⁺ enters either of the three possible sites: Li, Nb and structural vacancy (SV) site. The observed spectra can be resolved into (I) the main (Cr₁³⁺) and (II) the weak (Cr_II³⁺) spectra. The axial zero-field splitting parameter for a Cr³⁺ centre at Li site (D_Li) as well as Nb site (D_Nb) is calculated using the superposition model. The values D_Li and D_Nb agree well with the experimental D value for Cr_I³⁺ and Cr_II³⁺, respectively. This confirms that the main spectra can be attributed to Cr_I³⁺ at the Li site and the weak spectra to Cr_II³⁺ at the Nb site. For Cr³⁺ ion at the structural vacancy site the parameter D_SV is calculated as a function of displacement of Cr³⁺ ion from the centre of the oxygen octahedron along the [1 1 1] direction. Other weak and unresolve spectra also observed by us can possibly be due to Cr³⁺ centres at vacancy site. © 1993.