Large magnetic hysteresis in a melt-textured Y-Ba-Cu-O superconductor

Abstract

Melt-textured YBa2Cu3O7−δ superconductor with a long and well-aligned grain structure is shown to exhibit magnetic hysteresis at 77 K which is the largest ever reported for bulk polycrystalline Y-Ba-Cu-O. The large ΔM resulted in a magnet-like behavior as well as a strong suspension phenomenon. It is shown, contrary to the previous reports, that the suspension behavior observed in Y-Ba-Cu-O is a generic consequence of large grain size, and not due to the presence of Ag oxide or Ag particles. There appears to be no substantial enhancement in flux pinning and Jc by these particles. Comparisons of magnetization behavior in various YBa2Cu3O7−δ samples (polycrystals, silver-oxide doped, melt-textured, and single crystals) indicated that for applied fields substantially larger than Hc1 the current flow that gives rise to the observed magnetization is intragranular. The pinning force and hence the critical current is roughly the same [Jc (magn)∼104 A/cm2] within a factor of ∼2 regardless of grain size, grain boundary configuration, presence of second phase particles, or increased dislocation and twin densities.