PHASE-DIAGRAMS OF SPIN-3 2 ISING-MODEL ON A SQUARE LATTICE IN TERMS OF CORNER TRANSFER-MATRIX RENORMALIZATION-GROUP METHOD/

We obtain phase diagrams of a spin-3/2 Ising model on a square lattice by using a corner transfer matrix renormalization group method. We fi nd that three phases appear in the phase diagrams they are the ferroma gnetic(FM) phase, the paramagnetic(PM) phase and a ferrimagnetic(FI) p hase. It turns out that a tricritical point appears in a region of spa ce spanned by parameters of coupling constants and the temperature. We estimate values of critical exponent nu and alpha at a transition tem perature between the FM phase and the PM phase, at that between the FI phase and the FM phase, and also at that between the FI phase and the PM phase, by using the finite size scaling analysis.