MEAN-FIELD RENORMALIZATION-GROUP APPROACHES TO THE SURFACE ON A SEMIINFINITE ISING-MODEL WITH A RANDOM SURFACE FIELD

We study the critical behavior of the surface on a semi-infinite simple-cubic-lattice Ising model with a bimodal random surface field by a large-cell mean-field renormalization-group method. Our results show that a surface ferromagnetic phase exists at weak random fields above the bulk critical temperature, and no signs of the tricritical point are found until the surface critical temperature decreases to that of the bulk. © 1995 The American Physical Society.