Experimental and Theoretical Investigation of Spin‐Hamiltonian Parameters for the Low Symmetry Fe3+ Centre in LiNbO3

Abstract

AbstractX‐band EPR spectra of Fe3+ in LiNbO3 single crystals at room temperature are analyzed with a spin‐Hamiltonian of C3 symmetry. First the zero‐field splitting (ZFS) parameters b, b, b, and b−34 are calculated using the superposition model (SPM). The SPM‐ZFS results for Fe3+ at the Nb site agree better with the experimental ones than those for Fe3+ at the Li site. Next the crystal field (CF) parameters are predicted using SPM and two sets of available structural data for LiNbO3. Diagonalization of the full Hamiltonian, including the CF Hamiltonian, within the whole 3d5 configuration yields the ZF splittings for Fe3+ centres. The ZF splittings obtained from the theoretical SPM‐CF calculations for Fe3+ at the Nb site agree better with the experimental EPR data than those for Fe3+ at the Li site. The present results indicate that the observed EPR spectra of Fe3+ : LiNbO3 can be attributed to Fe3+ ions at the Nb sites.