EPR, ENDOR, and optical spectroscopy of the tetragonalYb3+center inKMgF3

Abstract

Electron paramagnetic resonance, electron-nuclear double resonance, and optical spectroscopy of the tetragonal Yb 3ϩ center in KMgF 3 are reported here. The results of these experiments allow us to conclude that a previously given structural model as well as the interpretation of the optical spectrum of this center are incorrect. A model is presented and experimentally and theoretically justified. In particular, the values of the hyperfine and transferred hyperfine interaction parameters were determined as well as an experiment-based energy-level scheme. Its parametrization is performed by including simultaneously the crystal field and the spin-orbit interaction within the 7 F term. Furthermore, a theoretical analysis of the transferred hyperfine interaction ͑THFl͒ parameters is presented. It is further shown from optics and from microscopic calculations of the THFI parameters that g ʈ and g Ќ have opposite signs and that the rule of correspondence between the cubic g factor and g ϭ 1 3 (g x ϩg y ϩg z) does not depend on the relative magnitude of the cubic and lowsymmetry crystal field acting on the rare-earth ion.

Theoretical Explanations of the Optical and EPR Spectra for Tetragonal Yb3+ Center in KMgF3 Crystal

“…For the tetragonal Yb 3+ center, a crystal-field analysis of the optical spectra was made. The calculated electronic energy levels are consistent with the observed values [8]. But by considering only the interaction within the ground 2 F 7/2 multiplets, the EPR g factors calculated from the firstorder perturbation formulae poorly agree with the experimental findings [7,8].…”

“…The calculated electronic energy levels are consistent with the observed values [8]. But by considering only the interaction within the ground 2 F 7/2 multiplets, the EPR g factors calculated from the firstorder perturbation formulae poorly agree with the experimental findings [7,8]. In addition, up to now no theoretical calculation of the hyperfine structure con- In this paper, we use the second-order perturbation formulae of EPR parameters for an 4f 13 ion in tetragonal symmetry.…”

“…Applying all these parameters to the energy matrix, and fitting the theoretical optical spectra to those observed [8], we can obtain the best fitting results of the crystal-field parameters and spin-orbit coupling coefficient for KMgF 3 :Yb 3+ crystal, i. e., …”

Zeeman splitting factor of the Er3+ ion in a crystal field

“…For instance, in case of axial symmetry, a real trace of g ii + 2g1 = -18, based on g 11 = + 1.2 and gl = -9.6 and derived from f, is measured as a trace of 20.4 and interpreted as having a F 6 origin. In rare cases only, negative g values have been concluded to for consistent analysis of experimental data, such as for the Yb ion in KMgF 3 [66]. Because of a complex dependence of g values on crystal field parameters a and ß, with often wide and sudden variations, the comprehensive summary of results is hard to give.…”

Effect of the f-Orbital Delocalization on the Ligand-Field Splitting Energies in Lanthanide-Containing Elpasolites

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] Theoretical modeling of such complexes involves high-cost methods because of the role of electron correlation and the necessity of taking into account the effects of the environment of the f-elements. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] Density-functional-theory methods based on the Kohn-Sham equations (KS-DFT) became standard tools in modeling large polyatomic systems. [30][31][32] In practice, KS-DFT calculations apply approximations to the exchangecorrelation functional and the associated potential which are usually rather adequate.…”