Superconductor/ferromagnet bilayers are known to exhibit nontrivial
dependence of the critical temperature T_c on the thickness d_f of the
ferromagnetic layer. We develop a general method for investigation of T_c as a
function of the bilayer's parameters. It is shown that interference of
quasiparticles makes T_c(d_f) a nonmonotonic function. The results are in good
agreement with experiment. Our method also applies to multilayered structures.Comment: 4 pages, 2 EPS figures; the style file jetpl.cls is included. Version
2: typos correcte