Investigation of the magnetic flux density distribution, current distribution and magnetization curve of Y-Ba-Cu-O thin films

In high quality Y1Ba2Cu3O7-x thin films with circular, triangular and quadratic shape, the magnetic flux density distribution (MFDD) and magnetization curve are measured. Comparison of calculated and measured MFDD shows good agreement and yields the critical current densities of the films. These jc-values agree with the jc-values calculated from the maximum magnetization which is reached at the external field μ0Hp'. Within the Bean model the field μ0Hp' should agree with the penetration field μ0Hp necessary for full flux penetration. The measurements show that μ0Hp' is smaller than μ0Hp by a factor of about 2. This is understood by taking into account a field dependent critical current density. Furtheron a formula is presented for the magnetic stray-field in the center of a regular polygon with homogeneous thickness which gives also the penetration field μ0Hp. (orig.)