Investigations on the spin Hamiltonian parameters for Gd3+ in YBa2Cu3O6+x

The spin Hamiltonian parameters [zero-field splittings (ZFSs) b(2)(0), b(2)(2), b(4)(0), b(4)(4), b(6)(0), b(6)(4) and the g factors] for the orthorhombic Gd3+ center in YBa2Cu3O6+x are theoretically investigated from the superposition model formulas for the ZFSs and the approximation formula of the g factors including admixture of the ground S-8(7/2) and the excited L-6(7/2) (L = P, D, F, G) states via the spin-orbit coupling interactions, respectively. The large anisotropy of the g factors in the (a, b) plane, originated from the anisotropy of spin susceptibility, is illustrated by the effective spin-orbit coupling coefficients zeta' in the a and b principle axis directions. The calculated ZFSs and the g factors show reasonable agreement with the observed values. (c) 2005 Elsevier B.V. All rights reserved.