Field history analysis of spin configurations in the random-field Ising model

We introduce a method for the analysis of spin configurations of Ising-type models exhibiting the return point memory. We define a function {Hs} = g(s(H)) which allows, starting from a spin configuration s(H) produced by the application of a field history from saturation state, to obtain the set of reversal fields {H-S} which are actually stored in the state and that-if applied as a field history-will reproduce the original state. This function allows to discriminate if a locally stable state can be reached by the application of an external field. This method is applied to the numerical study of ID random-field Ising model showing that there exists a correlation between low-energy and field-reachable configurations and indicating the possibility of determining the size of the set of the field-reachable states. (C) 2003 Elsevier B.V. All rights reserved.