Nonhomogeneous magnetic order in superconductor-ferromagnet multilayers

We study the possibility of a nonhomogeneous magnetic order [cryptoferromagnetic (CF) state] in heterostructures consisting of a bulk superconductor and a ferromagnetic thin layer, due to the influence of the superconductor. The exchange field in the ferromagnet may be strong and exceed the inverse mean free time. An approach based on solving the Eilenberger equations in the ferromagnet and the Usadel equations in the superconductor is developed. We derive a phase diagram between the cryptoferromagnetic and ferromagnetic states and discuss the possibility of an experimental observation of the CF state in different materials.