Wetting and layering transitions in magnetic films

Abstract

AbstractThe understanding of the surface effect on wetting and layering transitions was explained both theoretically and experimentally. Indeed, using different spin system models and different numerical and approximate methods such as mean field and effective field theories, real space renormalization technique and Monte‐Carlo simulations, it is found that the wetting and layering transitions depend on the nature of the surface magnetic field, the surface coupling strength, the surface crystal field, the geometry of surface, the in‐homogeneity of substrate and the quantum fluctuations at the surface. It is also found that the layering transition temperature increases or decreases as a function of the film thickness depending on the surface coupling values. The wetting transition temperature can be greater or smaller than the layering temperature. In the case of a variable surface crystal field, an order‐disorder layering reentrance is found with new critical exponents behaviour. The wetting phenomena are also influenced by the nature of the surface. In fact the intra‐layer transitions appear under the effect of an edge on the surface and/or corrugated surfaces. However, the intra‐layering transitions are found for a surface temperature above, which the surface and the intra‐layer surface occur. While the bulk layering and intra‐layering transitions appear above another finite temperature which is greater than the former one. Such result is not found in the case of a perfect surface. Beside this, and under the corrugation effect, the pre‐wetting phenomena and layering transitions occur at zero temperature, even in the case of a uniform magnetic field. In this case the wetting temperature depends strongly on the width of the corrugated‐steps but weakly on its number. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)