Electron–nuclear double resonance measurement of hyperfine interactions in Eu²⁺:CaWO₄

Abstract

The hyperfine interactions in Eu 2+ located substitutionally in CaWO 4 have been accurately measured at a temperature of 4.2 °K by the method of electron–nuclear double resonance. These measurements were made in an attempt to determine the effects of the crystal field on the hyperfine interactions by comparison with results obtained for atomic Eu and Eu 2+ in CaF 2 .The results have been fitted with a 12-parameter hyperfine Hamiltonian. Four of these parameters are used to represent an anisotropic quadrupole interaction and three to represent an anisotropic contribution of the form J 3 I. It is found that the spherically averaged quadrupole interaction is shifted by almost 20% from its value in CaF 2 . The nuclear g factor is also found to be shitted and anisotropic. These results are discussed in terms of a crystal-field induced shielding of the nuclear moments.