Microphase separation and modulated phases in a Coulomb frustrated Ising ferromagnet
Laboratoire de Physique Théorique des Liquides Université Pierre et Marie Curie, 4 place Jussieu, 75252 Paris Cedex 05, France
Accepted: 28 September 1998
We study a 3-dimensional Ising model in which the tendency to order due to short-range ferromagnetic interactions is frustrated by competing long-range (Coulombic) interactions. Complete ferromagnetic ordering is impossible for any nonzero value of the frustration parameter, but the system displays a variety of phases characterized by periodically modulated structures. We have performed extensive Monte Carlo simulations which provide strong evidence that the microphase separation transition between paramagnetic and modulated phases is a fluctuation-induced first-order transition. Additional transitions to various commensurate phases may also occur when further lowering the temperature.
PACS: 05.50.+q – Lattice theory and statistics; Ising problems / 05.70.Fh – Phase transitions: general aspects / 64.60.Cn – Order-disorder transformations; statistical mechanics of model systems
© EDP Sciences, 1998