Unique phase diagrams in ultra-thin Ising films with dilutions

•Phase diagrams are discussed for two nanoscaled Ising films.•By using the EFT, the effects of interlayer coupling on them are examined.•Some characteristic phenomena are obtained for two systems.•The unique behavior for the variation of critical concentration is reported.

The phase diagrams of two nanoscaled thin films with site (or bond) dilution, described by the spin-1 (or spin-1/2) Ising model, are investigated by the use of the effective field theory with correlations. They are consisted of two layers. Some unique features have been found in the phase diagrams, while they show many similar behaviors for both the spin-1/2 films and the spin-1 films with a positive single-ion anisotropy. It is clarified that the unique behavior of critical concentration in the spin-1 system with site dilution and a positive single-ion anisotropy at which the transition temperature reduces to zero is completely equivalent to that in the spin-1/2 system with site dilution.