FINITE-SIZE-SCALING IN ISING THIN-FILMS

The Curie temperature of Ising thin films with various crystalline str uctures and surface orientations is calculated within the Bragg-Willia ms and the Bethe approximations. T(c) is calculated as a function of t he number of layers N and the scaling relation DELTAtau = 1 - T(c)(N)/ T(c)(infinity) = AN(-lambda) is obtained. It is analyzed in detail how the coefficient A and the exponent lambda depend on the approximation used, on the crystalline structure, on the ratio between the surface and bulk coordination numbers, and how they tend to the asymptotic val ues.