Magnetization and ordering temperature of films and multilayers

We investigate, in this paper, a number of magnetic properties of single and multilayer thin film systems within the Ising model by application of mean field, finite cluster approximations as well as by Monte Carlo simulations. The magnetization profiles and the magnetic ordering temperature are calculated for different magnetic systems. The influence of corrugation and disorder at the surface, on the critical behavior of ferromagnetic Ising film is also studied. It is found that the critical surface exponent of the magnetization follows closely the one of a perfect surface, in the two cases: corrugated surface and random equiprobable coupling surface. However, in the case of flat surface with random interactions the surface critical exponent depends on the concentration of the strong interaction, while such critical exponent is independent on the concentration. Moreover, in the case of corrugated surface, the effective exponent for a given layer, is a function of the number of steps at the surface. The probability of a magnetic ground state is larger for low spatial dimensionality of an extended system, or lower for local symmetry of a given site in the atomic lattice. Consequently, the magnetic properties are usually more pronounced at the surface of a bulk magnet as compared to the bulk interior. The phase diagram and the characteristic behaviors of the surface magnetization, are investigated for amorphous or cristalline surfaces. Indeed, the size effects become more relevant at low temperature depending on film thickness.