Size effects in frustrated dipolar spin systems

The effect of classical dipole interactions on the paramagnetic to glass phase transition is studied in three- and quasi-two-dimensional site-disordered Ising spin systems. A field theory is developed using a Gaussian variational approach to estimate transition temperatures and study phase stability. Long-range dipolar interactions are found to permit a transition to the glass state. An investigation of the role of relative length scales within the model highlights restrictions on the existence of the glass phase in the two-dimensional case, and this effect is shown to be sensitively dependent on Ising spin geometry.