Characteristic behaviors in an ultrathin Ising film with site- (or bond-) dilution at the surfaces

The phase diagram, magnetization and Arrott plot of an ultrathin film with site or bond dilution at the surfaces are investigated by the use of the effective field theory with correlations (or the mean field theory for comparison). The system is consisted from the two Ising layers. A lot of characteristic phenomena can be found in them. In particular, the behaviors of them are completely different, depending on whether the site or bond dilution is performed at the surfaces. A lot of unexpected phenomena, such as a new type of frustration, have been obtained in the phase diagram and magnetization, when the strength of interlayer coupling between the two layers is changed.