The spontaneous formation of a vortex structure in a type II superconductor-ferromagnet bilayer

The conditions for the formation of a vortex structure in a thin supercondu cting film under the action of a stray field of stripe domain structure of a uniaxial ferromagnet are determined. The critical magnetization of the ma gnetic material is calculated, above which the mixed state of the supercond uctor becomes energetically favored over the Meissner phase. It is shown th at the critical magnetization decreases monotonically with decreasing thick ness of the superconducting film and is of the order of ten gauss in typica l actual situations. The critical-current anisotropy in a superconducting f ilm with an induced vortex structure is discussed qualitatively. (C) 2001 M AIK "Nauka/ Interperiodica".