Field induced anti-nematic ordering in assemblies of anisotropically polarizable spins

We investigated the effects of dipolar interactions in a lattice system of anisotropically polarizable particles in the presence of external field both by a Montecarlo computer simulation and through a mean field analysis. In a specific range of low temperatures, large external field and large particle density, a novel anti nematic structure is found, in which the system spontaneously splits into two intercalated sublattices characterised by different orientational orders: on each plane perpendicular to the field, a chessboard of spins aligned along and perpendicularly to the field is found. First and second order phase transition lines, connected at a tri-critical point, enclose the anti nematic phase in the temperature-density plane.