Study of the special point in the surface phase diagram of a semi-infinite Ising ferromagnet

The phase diagrams of the semi-infinite Ising ferromagnet with decorated magnetic (spin-S) and nonmagnetic atoms on the surface are investigated within the framework of the effective-field theory. In particular, the critical properties of the special point in the surface phase diagram are examined numerically by changing the coupling constants, the single-ion anisotropy constant D on the spin-S (S>12) atom, the value of S and the concentration p of magnetic atoms. We find many characteristic features in the behaviour, such as the phenomenon depending on whether S is a half-integer or an integer.