The trigonal paramagnetic Yb3+ ion in SrF2 is investigated. The analysis used EPR and optical spectroscopy. The energy level scheme of the center is determined from its optical spectra and the parameters of the crystal field potential are calculated

Bill H.

Falin M.

Gerasimov K.

Leushin A.

Lovy D.

Sanadze T.

Journal of Alloys and Compounds

Kazan Federal University Digital Repository

LJournal of Alloys and Compounds 323–324 (2001) 692–695www.elsevier.com/ locate / jallcom31EPR and optical spectroscopy of SrF doped with Yb2a , a b c c d*M.L. Falin , K.I. Gerasimov , A.M. Leushin , H. Bill , D. Lovy , T. SanadzeaZavoisky Physical-Technical Institute, 420029 Kazan, RussiabKazan State University, 420008 Kazan, RussiacGroup PCB, University of Geneva, 1211 Geneva 4, SwitzerlanddTbilisi State University, 380028 Tbilisi, GeorgiaAbstract31Results of EPR and optical spectroscopic investigation of the trigonal paramagnetic Yb ion in SrF (‘oxygen’ paramagnetic center —2T ) are presented. The energy level scheme of the center is determined from its optical spectra and the parameters of the crystal field2potential are calculated. Ó 2001 Elsevier Science B.V. All rights reserved.Keywords: Insulators; Crystal growth; Point defects; Crystal and ligand fields; EPR and optical spectroscopy1. Introduction PCs in SrF and BaF crystals may be increased to three.2 2This process is controllable providing additional means forIt is known that depending on the conditions of crystal identification of the spectral lines. The structural models31synthesis, the Yb ion in a CaF single crystal forms up have been experimentally established, by the radiofrequen-2to 13 paramagnetic centers (PC) with different symmetry cy discrete saturation method (analogous to ENDOR) [2–31[1]. The Yb ion in this matrix has been extensively 4]. In the PbF host, only one cubic PC is usually observed2studied by EPR, ENDOR and optical spectroscopy (includ- [1], although there is a report that a trigonal PC may alsoing Zeeman spectroscopy). Yet, considerable discrepancies exist [6].in the interpretation of the optical absorption and lumines- In view of these facts, we chose to study those systemscence spectra of the PCs still remain, and the Stark which show a minimum number of PCs. This paperstructures of these centers are not unambiguously iden- presents EPR and optical spectroscopy results on the T231 31tified. Systematic optical data for Yb in crystals of the center formed by the Yb ion in SrF . Data from231homologous series MeF (Me5Sr, Pb, Ba) are practically preliminary optical experiments on BaF :Yb were pub-2 2absent. In comparison with the CaF lattice, a considerable lished in an earlier paper [7].2decrease in the number of PCs with different symmetries isobserved in these latter systems and the study of theiroptical spectra may thus enable an unambiguous identifica-tion of some of them. As-grown crystals of SrF and BaF 2. Experimental results and discussion2 231show two Yb PCs: a cubic one (non-local compensationof the excess positive charge) and a trigonal one [1]. In the SrF :Yb crystals were grown by the Bridgman method2latter case, the excess positive charge is compensated by an in graphite crucibles in a fluorine atmosphere. Someadditional fluorine ion located in the center of the normally crystals were subsequently hydrolyzed during several31empty cube next to Yb along a C -axis (this is the hours according to the method described [8]. EPR experi-3so-called ‘fluorine’ trigonal PC — T ). By special thermal ments were carried out on an X-band spectrometer at 4.2,4treatment (hydrolysis) these PCs may be partially trans- 77 K. Optical spectra were recorded at T52, 300 K on aformed into a trigonal ‘oxygen’ PC (T ), where the oxygen home built multifunctional computerized spectrometer [7].2ion substitutes one of the fluorine ions in the nearest cubic A cooled photomultiplier formed the detector, and the light31environment of Yb [5]. Thus the number of different from a xenon lamp dispersed by a monochromator wasused as an excitation source. The luminescence andexcitation spectra were recorded by time delayed (strobo-*Corresponding author. Fax: 17-8432-765-075.E-mail address: falin@kfti.knc.ru (M.L. Falin). scopic) detection.0925-8388/01/$ – see front matter Ó 2001 Elsevier Science B.V. All rights reserved.PI I : S0925-8388( 01 )01040-4

EPR and optical spectroscopy of SrF2 doped with Yb3+

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EPR and optical spectroscopy of SrF2 doped with Yb3+

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