PHASE-TRANSITIONS IN THE SPIN-3 2 BLUME-EMERY-GRIFFITHS MODEL/

The spin-3/2 Ising model on the square lattice with nearest-neighbor f erromagnetic exchange interactions (both bilinear (J) and biquadratic (K)) and crystal-field interaction (DELTA) is studied using a renormal ization-group transformation in position-space based on the Migdal-Kad anoff recursion relations. The global phase diagram in (J, K, DELTA) s pace (with J, K greater-than-or-equal-to 0) is found to have two surfa ces of critical phase transitions and two surfaces of first-order phas e transitions. These surfaces are variously bounded by an ordinary tri critical line, an isolated critical line of end points, and a line of multicritical points. The global connectivity and local exponents of t he thirteen separate fixed points underlying this quite complicated st ructure are determined.