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EPR Study of Low Symmetry Mn 2+ Centers in LiNbO 3 . Superposition Model and Crystal Field Analysis of the Zero‐Field Splitting Parameters
Author(s) -
Yeom T. H.,
Choh S. H.,
Chang Y. M.,
Rudowicz C.
Publication year - 1994
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221850212
Subject(s) - superposition principle , electron paramagnetic resonance , zero field splitting , spectral line , hamiltonian (control theory) , ion , zero (linguistics) , field (mathematics) , crystal (programming language) , symmetry (geometry) , chemistry , crystal field theory , condensed matter physics , physics , crystallography , molecular physics , nuclear magnetic resonance , quantum mechanics , mathematics , electron , geometry , spin polarization , mathematical optimization , linguistics , philosophy , computer science , pure mathematics , programming language
X‐band EPR spectra of Mn 2+ : LiNbO 3 single crystals at room temperature are analyzed with a spin‐Hamiltonian of C 3 symmetry. Experimental data are interpreted using the superposition model in a twofold way. Firstly, the zero‐field splitting (ZFS) parameters b 2 0 , b 4 0 , b 4 3and b 4 −3 are predicted. While the results for b 2 0are not conclusive, those for the major fourth‐order ZFS term | v 4 3 | = [( b 4 3 ) 2 + ( b 4 −3 ) 2 ] 1/2 indicate better agreement with experiment, assuming Mn 2+ at the Nb site. Secondly, crystal field (CF) parameters are obtained from the superposition model using two sets of available structural data. Diagonalization of the CF Hamiltonian within the whole 3d 5 configuration yields the theoretical ZF splittings. The results for Mn 2+ at the Nb site agree better with the experimental data than those for Mn 2+ at the Li site. Hence the superposition model analyses of the observed EPR spectra indicate that the spectra can be most likely attributed to Mn 2+ ions at Nb sites. The ways to reconcile this conclusion with the opposite one from the low temperature ENDOR study are discussed.