Onset of flux penetration into a type-I superconductor disk

Virgin magnetization of a superconducting disk in a transverse magnetic field is discussed. A field in which a metastable state arises in samples due to the geometrical barrier is calculated on the base of both the Landau theory of the intermediate state and the Hao-Clem description of the mixed state. It was found that this field agrees well with the penetration field measured for thin flat samples of type-I superconductors with weak pinning.