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

Abstract

. R u~o w~c z~) (a) X-band EPR spectra of Fe3+ in LiNbO, single crystals at room temperature are analyzed with a spin-Hamiltonian of C, symmetry. First the zero-field splitting (ZFS) parameters b:, bt, b:, and b4 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 LiNbO,. Diagonalization of the full Hamiltonian, including the C F Hamiltonian, within the whole 3d5 configuration yields the ZF splittings for Fe3 + centres. The Z F 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+ : LiNbO, can be attributed to Fe3+ ions at the Nb sites.

The relationship between the g-shift and the local structure for the axial impurity centers in the doped LiNbO3 crystals

“…The results of calculation using the superposition model (SPM) for zero-field splitting parameters (ZFS) b 0 2 , b 0 4 , b 3 4 and b −3 4 for both above centers in lithium niobate crystals are presented in Refs. [21,22]. Additionally we analyze other axial Fe 3+ center in LiNbO 3 :Fe reported by Malovitchko et al [23].…”

“…We are focused on analyzing 6 S state Fe 3+ [21] and Mn 2+ [22] ions in LiNbO 3 . The results of calculation using the superposition model (SPM) for zero-field splitting parameters (ZFS) b 0 2 , b 0 4 , b 3 4 and b −3 4 for both above centers in lithium niobate crystals are presented in Refs.…”

EPR spectra and local lattice structure of Fe3+ impurity ions in ferroelectric LiNbO3

“…However, at the present time there is no satisfactory and quantitative unified explanation for the optical absorption and EPR spectra, and the local structure of Fe 3+ in LiNbO 3 crystal. Further, the reported values of the spin-Hamiltonian (SH) parameters obtained from EPR of Fe 3+ in LiNbO 3 are not uniform because of the different experimental conditions and crystal composition [12][13][14][15][16]. Grachev et al [17] has advanced that the spin-Hamiltonian parameters are dependent on the temperature.…”

NMR spin-lattice relaxation study of 7Li and 93Nb nuclei in Ti- or Fe-doped LiNbO3:Mg single crystals

“…11,12 Transition-metal and rare-earth dopant ions play important roles in most of the applications of LiNbO 3 . Many studies have been performed on Fe 3+ -doped LiNbO 3 crystals, [13][14][15][16][17][18][19][20][21][22][23][24] while only a few studies have investigated LiNbO 3 Co-doped with Fe 3+ and Mg. 25,26 However, it was found that the Fe 3+ ions entered the Li sites, [14][15][16] as well as the Nb sites. 13,14,23,24 This ambiguous site assignment may arise from the very similar environments of the cation sites; both the Li + and Nb 5+ ions lie in slightly distorted O octahedra with a C 3 site-symmetry.…”