FLUX-PINNING AND CRYSTAL-FIELD MAGNETOSTRICTIONS IN REBA(2)CU(3)O(7-X) HIGH-T-C SUPERCONDUCTORS

High-field (up to 12 T) magnetostriction measurements have been performed on single crystals of REBa(2)Cu(3)O(7-x) (RE = Dy, Ho and Er) at the paramagnetic and superconducting phase, between 3.8 and 100 K. Low-temperature contributions to the shape magnetostriction, related to the vortex flux pinning, are found evidence for, through the strong hysteresis shown by the magnetostriction isotherms. This flux-pinning magnetostriction shows a scaling behavior which has been analyzed in terms of Kramer's flux-lattice shear stress model, and represents a new method to study pinning mechanisms using magnetostriction measurements. We have also isolated the single-ion crystal electric field (CEF) origin basal plane symmetry breaking magnetostrictive mode. epsilon(gamma) (congruent to-300X10(-6) at 10 K and 12 T, for Dy and Ho compounds), obtaining the ratio M(gamma)/C-0(gamma) (=1.3X10(-4), for the Ho compound and approximate to 5X10(-4), for the Dy compound) where M(gamma) is the single-ion CEF irreducible coupling parameter and C-0(gamma) the paramagnetic symmetry elastic constant. The obtained quadrupolar coupling parameter G(gamma) for the Ho compound is -35 mK/ion.