Calculation of the spin-lattice coefficients of Gd3+ in caF2 using a point-charge model for the crystalline fieId.

Abstract

The contribution of the Blume-Orbach mechanism to the second-order spin-lattice coefficients for Gd3* in cubic sites of CaF2 has been calculated with a point-charge approach for the orbit- lattice interaction. Our results, G3g (2) = - 0. 006 cm"1 and G5g (2) = - 0.07cm 1, agree in sign with the experimental values of G3g (2) = — 0. 22cm"1 and G¡£} = — 0.11 cm 1. Differences in magnitude of G5g (2) can be understood in view of the opposite contribution of the fourth- and sixth-order terms of the orbit-lattice Hamiltonian. We conclude that the Blume-Orbach mechanism predicts values for the spin-lattice coefficients G3g (2) and G5g (2) of Gd3* in CaF2 in reasonable agreement with the experimental data, and that the cubic crystalline field must be considered in any calculation of the spin- lattic parameters.