How does mean-field theory work in magnetic multilayer systems?

Phase transition and critical phenomena in magnetic multilayer systems are studied in terms of Ginzburg-Landau mean-field theory. Detailed calculations are carried out for a system consisting of a layer of finite thickness coupled to a semi-infinite bulk magnet. Correlation functions are derived and the shift in critical point with the overlayer thickness and coupling between the neighboring layer is evaluated. A new critical exponent ν̃=1 is derived for the divergence of the effective extrapolation length at the interface with temperature and/or layer thickness.