Effects of Cation Substitution on the Magnetization for Bi-2212 Phase

Abstract

Effects of various cation substitutions on the pinning properties of the Bi-2212 phase have been investigated. It has been found that the substitution of Y or rare earth element for (Sr, Ca) or Pb for Bi improves the pinning properties, while changes in oxygen content influence only slightly. The former substitution does not, however, change the irreversibility line, suggesting that the enhancement of the pinning is due to point like defects as in the case of the background pinning. The latter substitution improves the irreversibility line at high temperatures. In this case the pinning centers introduced are considered to be larger in size and possibly caused by the structural transformation between orthorhombic and monoclinic phases giving rise to a some kind of lattice distortion.