Temperature-induced domain shrinking in ising ferromagnets frustrated by a long-range interaction

Abstract

We investigate a spin model in which a ferromagnetic shortrange interaction competes with a long-range antiferromagnetic interaction decaying spatially as 1/rd+δ, d being the dimensionality of the lattice. For δ smaller than a certain threshold δ̂(with δ̂ 1), the long-range interaction is able to prevent global phase separation, the uniformly magnetized state favored by the exchange interaction for spin systems. The ground state then consists of a mono-dimensional modulation of the order parameter resulting in a superlattice of domains with positive and negative magnetization.We find that the period ofmodulation shrinks with increasing temperature T and suggest that this is a universal property of the considered model. For d = 2 and δ = 1 (dipolar interaction) Mean-Field (MF) calculations find a striking agreement with experiments performed on atomically-thin Fe/Cu(001) films. Monte Carlo (MC) results for d = 1 also support the generality of our arguments beyond the MF approach. © 2009 ICST Institute for Computer Sciences, Social Informatics and Telecommunications Engineering.