GINZBURG-LANDAU THEORY OF SUPERCONDUCTOR-FERROMAGNET HETEROSTRUCTURES

On the basis of a Ginzburg-Landau theory for two coupled order parameters, we investigate heterostructures of superconducting and ferromagnetic materials coupled via the proximity-effect. We study a bilayer and a sandwich-like geometry both extending to infinity. Without an external magnetic field but fully taking into account the nonlinearities, we obtain phase diagrams and temperature dependent order parameter profiles as well as corresponding free energies. In this mean field theory, we find reentrant behavior and the occurrence of first order phase transitions. We also derive relationships between different geometries.