The study of a critical state in YBa2Cu3O7−δ superconductors with a large demagnetization factor by 3-D neutron polarization analysis

The trapped magnetic flux distribution was studied in thin flat superconducting samples of 1-2-3 compound having both a large demagnetization factor and a high edge barrier for vortex entry and exit. A three-dimensional analysis of neutron polarization was used to obtain the distribution patterns. It is shown that the nature of the critical state in polycrystalline wafers, unlike that in a ceramic wafer, is not described by the Bean model.