Spectroscopic analysis of lithium terbium tetrafluoride

H.P. Christensen

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Abstract

The absorption spectra of Tb3+ in LiTbF4 have been recorded in the spectral interval from 4000 to 25000 cm-1 and for temperatures between 2.3 and 150 K. This covers the transitions from the ground multiplet 7F6 to the multiplets 7F3, 7F2, 7F1, 7F0, and 5D4. The transitions were predominantly of electric-dipole nature, but small contributions of magnetic-dipole nature were seen. The crystal-field splitting was temperature dependent—the reason for this is not completely understood. No experimental evidence for a crystallographic phase transition was found. The energy levels of the ground 7F term were calculated by diagonalizing an effective spin-orbit and crystal-field Hamiltonian in an LS basis. H=Σλi(L→·S→)i+ΣαiΣBimOim, where the parameters λi are functions of the spin-orbit parameter ζ and the Slater parameter F2. The Oim and αi are Racah operators and reduced matrix elements, respectively. The rare-earth site in LiTbF4 possesses S4 symmetry, which allows six crystal-field parameters. ζ and the six Bim were varied to obtain the best agreement with the experimentally observed levels. Keeping F2=434 cm-1 fixed, a fit with a standard deviation of 12 cm-1 was obtained at 10 K with the following parameters: ζ=1698 cm-1, B20=445 cm-1, B40=-761 cm-1, B44=1120 cm-1, B60=4 cm-1, and B64=761+i609 cm-1. Although the ground LS term of Tb3+ is rather isolated, the term mixing is significant, which is also the case for the multiplet mixing. Even for the ground multiplet the J mixing cannot be ignored.
Original languageEnglish
JournalPhysical Review B
Volume17
Issue number10
Pages (from-to)4060-4068
ISSN2469-9950
DOIs
Publication statusPublished - 1978

Bibliographical note

Copyright (1978) by the American Physical Society.

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