Endor of ¹⁷³ Yb ³⁺ on tetragonal sites in calcium fluoride: determination of the crystal field parameters

Abstract

Endor experiments have been performed on 173 Yb at tetragonal sites in CaF 2 . The spin-Hamiltonian describing the frequencies of the endor lines contains many small terms, which arise in second order from matrix elements of Zeeman and hyperfine interactions that couple the ground doublet to excited states of the J = 7/2 manifold. From the experimental values of these small terms the energies of the excited states of this manifold are deduced. This information is used together with g values of the lowest doublet for both J = 7/2 and J = 5/2 manifolds, and the energy of the lowest doublet of the J = 5/2 manifold, to calculate the following crystal field parameters (all in cm -1 ): B 2 0 = + 8.4 ( 1.3 ) ; B 4 0 = + 0.19 ( 0.03 ) ; B 6 0 = + 0.054 ( 0.005 ) ; B 4 4 = + 2.8 ( 0.4 ) ; B 6 4 = − 0.735 ( 0.07 ) . . The measured value of the nuclear electric quadrupole interaction for 137 Yb( I = 5/2) is sepa­rated into a component due to the field gradient from the 4f electrons and one due to the field gradient from the surrounding lattice. Comparison of the latter component with the value of B 2 0 gives (1–γ∞)/(1–σ 2 ) = 75±18, considerably smaller than values of this ratio predicted theoretically or found in earlier experimental investigations. The most likely cause of this low value is the considerable contribution of covalent effects to B 2 0 .

Direct imaging of rare-earth ion clusters inYb:CaF2

“…3 and 4). But the same authors calculate this tetragonal second sublevel at 229 cm −1 , which is not so far from the experimental 164 cm −1 reported by Baker and Blake [38]. Because of this uncertainty, we choose a weight of 0 for this level.…”

Electron paramagnetic resonance enhanced crystal field analysis for low point-group symmetry systems: C2vsites in Sm3+:CaF2/SrF2

“…The two dominant interactions of the free-ion Hamiltonian are the electrostatic repulsion and the spin-orbit interaction. We follow Carnall et al [25] in defining the free-ion Hamiltonian by 3,4,6,7,8…”

“…Accurate crystal-field calculations of magnetic and hyperfine interactions for rare-earth ions in low point-group symmetry systems is a difficult problem [1,2]. While previous studies have employed ground-state g values to enhance crystal-field calculations [2][3][4][5][6], accurately reproducing magnetic and hyperfine interactions for low point-group symmetry systems is still challenging. Crystal-field models for low-symmetry materials such as yttrium orthosilicate have potential to aid in the development of the many recently demonstrated rare-earth ion based applications employing low-symmetry host materials.…”