FLUX-PINNING IN MELT GROWN LRE123 SUPERCONDUCTORS

Unlike Y123 which forms only a stoichiometric compound the light rare earth elements (LRE: La, Nd, Sm, Eu, Gd) form a solid solution LRE(1+x )Ba(2+x)Cu(3)O(y). When LRE123 superconductors are melt-processed in a reduced oxygen atmosphere, they exhibit high T-c's and large J(c) val ues in high magnetic fields associated with a second peak effect. We b elieve that such a behavior is closely related to the presence of a LR E-Ba solid solution. In this paper we propose the flux pinning mechani sm of LRE 123, and then discuss the source of the peak effect.