Landau-Ginzburg theory for phase transitions in magnetic-superconducting sandwiches

Abstract
The phase diagram of a magnetic-superconducting sandwich below the Curie temperature of the magnetic side is considered. A coupling parameter between the two order parameters is determined from the microscopic properties. For strong coupling the superconducting transition is first order. It is shown that one is always in the weak-coupling limit when the magnetic material has localized spins.