Surface magnetism of a semi-infinite decorated Ising system

Magnetic properties of the surface in a semi-infinite decorated Ising system with a random field at a decorated site are investigated by the effective-field theory. In particular, the phase diagram and magnetization curves for the bulk and surface of the simple cubic ferromagnetic (or ferrimagnetic) system with a (0 0 1) surface are examined numerically. We find a lot of characteristic features in them, such as the reentrant phenomenon, the possibility of two compensation points on the surface and unexpected magnetization curves at or near the surface associated with it.