  We theoretically study the proximity effect in the thin-film layered
ferromagnet (F) - superconductor (S) heterostructures in F$_1$F$_2$S design. We
consider the boundary value problem for the Usadel-like equations in the case
of so-called "dirty" limit. The "latent" superconducting pairing interaction in
F layers taken into account. The focus is on the recipe of experimental
preparation the state with so-called solitary superconductivity. We also
propose and discuss the model of the superconducting spin valve based on
F$_1$F$_2$S trilayers in solitary superconductivity regime.
