Multicritical points in the ferromagnetic binary Ising model

The phase diagram and the temperature dependence of the magnetization of the random-site binary ferromagnetic Ising model consisting of spin-12 and spin-1 components in the presence of crystal-field interactions is investigated by the use of a mean field theory. By considering in this simple system all the exchange interactions positive, seven topologically different types of phase diagrams are achieved, including a variety of multicritical points such as tricritical, fourth-order, critical end, and isolated critical. An ordered phase persisting for large values of the crystal-field interaction is also observed.