Critical behaviour of the semi-infinite spin-2 Ising model

Abstract

Using the Migdal–Kadanoff renormalization group approach, we studied the three-dimensional semi-infinite spin-2 Ising model. Initially, we plotted the phase diagrams of the infinite spin-2 model in the bidimensional and tridimensional cases, where the system exhibits first- and second-order phase transitions and a tricritical point. Based on the ratios of bulk interactions to surface ones, three generic types of surface phase diagrams were identified, marked by tricritical behaviour and interesting second-order phase transitions, particularly ordinary, extraordinary, surface, and special transitions.