Surface Effects On Wetting and Layering Transitions

Wetting phenomena plays an interesting role in the technological development of materials. Recently, much attention has been directed to the study of magnetic solid films. To understand, theoretically, the effect of surface on wetting and layering transitions in these systems, we will give in this chapter a presentation of several relevant recent theoretical works realized on wetting and layering transitions in which we explain how the nature of surface can affect the behavior of wetting and layering transitions. Using different spin systems models and different numerical and approximate methods such as mean field and effective field theories, real space renormalization group technique, transfer matrix method 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. Indeed the layering transition temperature increases or decreases as a function of the thickness of the film depending on which the surface coupling is smaller or greater than a critical value. Thus the wetting transition temperature can be greater or smaller than the layering temperature. In the case of variable surface crystal field an order-disorder layering reentrance appears with new critical exponents and multi-critical behaviors. Wetting phenomena is also influenced by the curvature of the surface. In fact the intra-layers transitions appear under the effect of edge on the surface and/or corrugated surface. However, there exist an intra-layering surface temperature above which the surface and the intra-layer surface transitions occur . While the bulk layering and intra-layering transitions above an other finite temperature which is greater than the former one. Such behavior is not seen 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. The quantum fluctuations introduce a new wetting transitions, namely the wetting, layering and roughening transverse fields. These fluctuations lead to the appearance of a sequence of layering sublimations transitions which occur before bulk melting above a critical transverse field which depends on temperature and/or chemical potential. Moreover, the wetting temperature depends strongly on the randomness of the quantum fluctuations. The chapter is organized as follows: Section 1 is reserved to the Introduction and definitions. In section 2 we present Corresponding author : [email protected] Editor