Surface coupling effect on wetting and layering transitions

The effect of both surface coupling Js and surface magnetic field Hs on the dependency of the layering temperature TL as a function of the thickness N , of a spin−1/2 Ising film is studied using mean field theory. It is found that for Js greater than a critical value (Jsc = 1.30), the layering temperature decreases when the film thickness N increases for any values of Hs. While, for Js < Jsc, the behavior of the layering temperature TL as a function of N depends strongly on the Hs values. Indeed, we show the existence of three behavior classes of TL, as a function of the film thickness N , separated by two critical surface magnetic fields Hsc1 and Hsc2, namely: (i) for Hs < Hsc1, TL increases with N ; (ii) for Hsc1 < Hs < Hsc2, TL increases for small values of N , and decreases for large value ones; (iii) while for Hs > Hsc2, TL decreases with increasing the film thickness. It is also found that the wetting temperature Tw(Tw = TL when N → ∞), can be greater or smaller than the layering temperature of a film of thickness N , depending both on the values of Hs and Js. 1 ———————————– PACS :75.10.Jm; 75.30.Ds (*) Corresponding author: [email protected]