Circular phase of a two dimensional ferromagnet with dipolar   interactions
  We make for the first time a large-scale Monte-Carlo simulation of a ferromagnetic Heisenberg model with dipolar interactions on a two dimensional square lattice with open boundaries using an efficient new technique. We find that a phase transition occurs in the model and the ordered phase is characterized by a circular arrangement of the spins. 
Fumitaka Matsubara and Junya Sasaki