The site-diluted spin- Ising film

The phase transitions of a diluted spin- Ising film are examined using the framework of the effective field theory with a probability distribution technique that accounts for the single-site spin correlations. The critical temperature Tc/J of the system is calculated as a function of the thickness of the film, the concentration c of magnetic atoms and the ratio R=Js/J of the surface constant couplings to the bulk ones. It is shown that for R=Js/J less than a critical value Rc, the critical temperature of the film Tc/J is smaller than the bulk critical temperature TcB/J and for R Rc, Tc/J is larger than the bulk TcB/J and surface TcS/J critical temperatures of the corresponding semi-infinite system and as the film thickness L is increased further, for R Rc (R Rc), Tc/J increases (decreases) and approaches asymptotically for large values of L the bulk critical temperature TcB/J (the surface critical temperature TcS/J) of the corresponding semi-infinite system