SURFACE CRITICAL-BEHAVIOR OF THE SEMIINFINITE BLUME-EMERY-GRIFFITHS MODEL

Phase transitions of the three-dimensional semi-infinite Blume-Emery-G riffiths model, extended to negative biquadratic interactions, are inv estigated within the framework of the mean-field approximation in comp arison with the real-space renormalization-group results found previou sly. All the possible qualitative types of phase diagrams characterizi ng phase transitions of the model, including high entropy ferrimagneti c and staggered quadrupolar phases, have been determined. It is shown that such a system can exhibit critical and tricritical behavior on th e surface and multicritical points. [S0163-1829(97)05937-7].