Low-field structure in the magnetization of polycrystalline YBa2Cu3O7−x and ErBa2Cu3O7−x

Abstract
We have studied the structure present at small fields (2Cu3O7−x and ErBa2Cu3O7−x. This structure is absent from measurements on a powder of YBa2Cu3O7−x. We conclude that the structure results from interactions among the grains and is not an intrinsic property of the compounds. Flux creep associated with this structure is found to be proportional to ln(t) over three decades of observation time.