Thermodynamical properties of the mixed spin Blume-Capel model with four-spin interactions

A mixed spin Blume-Capel model consisting of spin-1/2 and spin-1 with four-spin interactions and crystal field interaction is studied by the use of the finite cluster approximation based on a single-site cluster theory. In this approach, the state equations are derived for the two dimensional square lattice. In addition to the phase diagrams and magnetizations which show a variety of interesting features, the influence of the four-spin interaction on the internal energy, specific heat and zero-field magnetic susceptibility is also examined.