Paramagnetic resonance of divalent europium in lead chloride

Abstract

Paramagnetic resonance spectra of Eu2+ ions at Pb2+ sites in PbCl2 were measured at room temperature and 3 cm wavelength. The point group symmetry at a Pb2+ site is monoclinic. Apart from a reflection, all sites in the unit cell are magnetically equivalent. Analysis yielded the following values for the dominant parameters in the spin Hamiltonian: g = 1.993 ± 0.003 isotropic b02 = (+107 ± 1) × 10-4cm-1b22 = (-527 ± 2) × 10-4cm-1 The z-axis is along the crystallographic a axis, x and y axes 23.5° from the crystallographic b and c axis respectively. In order to obtain a fit with the measured hyperfine structure for 151Eu terms Σi A′S3iIi are added to the spin Hamiltonian. The values for the HFS parameters are (in units 10-4cm-1): 151Ax = -31 ± 1 151A′x = -0.10 ± 0.02151Ay = -33.0 ± 0.5 151A′y = +0.10 ± 0.02151Az = -33.6 ± 0.5 151A′z = +0.11 ± 0.02153Q1 = +0.33 ± 0.06|153Q2| = +3.8 ± 0.1 The results are interpreted in terms of crystal field theory. Evidence is presented indicating that the second degree crystal field splittings found are mainly linear in the field strength. Under the assumption that a perturbation mechanism, linear in field strength and cubic in spin-orbit coupling, is mainly responsible for the second degree crystal field splittings, a value is derived for the electronic shielding coefficients γ∞ and γ2. The result is (1 − γ∞)/(1 − γ2) = +169, in reasonable agreement with present theoretical estimates.