Dynamic relativistic crystal field contributions to the values of the fourth-order spin-Hamiltonian parameter for Gd3+ in cubic and octahedral coordination

Based on the concept of the relativistic bilinear orbit-lattice interaction , phonon contributions to the values of the fourth-order spin-Hamiltonian p arameters for S-8(7/2) ground-state ions in diamagnetic lattices are discus sed. Useful explicit formulae allowing the estimation of the role played by lattice vibrations are derived. In particular, it is shown that for the ca se considered, phonon contributions should be more pronounced for six-fold coordinated complexes than for eight-fold ones. This conclusion is in good agreement with experimental data for fluoroperovskites and fluorides doped with Gd3+. (C) 1999 Elsevier Science B.V. All rights reserved.