Re-entrant ferromagnetism in a two-dimensional mixed spin Ising model with random nearest-neighbour interactions

Abstract

Using the finite cluster approximation we study a mixed spin model with random interactions on a ferrimagnetic square lattice (with spins σ=1/2 andS=1). The interactions are assumed to be independent random variables with distribution,P(K ij )=pδ(K ij −K)+(1−p) δ(K ij −αK), whereK>0 and |α|≦1. In a certain range of negative values of α the phase diagrams exhibit re-entrant behaviour. This indicates that re-entrance seems to be a characteristic feature of systems in which both frustration and disorder are present.