Instabilities in Ising systems with short- and long-range-correlated quenched random fields

Abstract

The ferromagnetically ordered states of Ising systems with short-range-correlated random fields are shown to be unstable with respect to domain formation for dimensionalities dl=2. Domain wall roughening for 2-a for large separation r. For a>d the same results as for short-range field correlations are found. For al=2 and wall roughening for aor=5) and a<d(d<5). The borderline value for a above which the mean-field theory is valid is found to be six. Experimental consequences of these results are indicated.