Ground state of the spin-1/2 Heisenberg antiferromagnet on a   two-dimensional square-hexagonal-dodecagonal lattice
  Up to now, the existence of the the magnetic Neel Long Range Order (NLRO) in nearest neighbor, spin-1/2 antiferromagnetic (AF) lattice systems has been examined for seven, from the eleven existing, two-dimensional, uniform lattices. Plaquettes forming these uniform (Archimedean) lattices (e.g. square, triangular, kagome) are different regular polygons. An investigation of the NLRO in the ground state of AF spin systems on the seventh uniform (bipartite) lattice consisting of squares, hexagons and dodecagons is presented. The NLRO is shown to occur in this system. A simple conjecture concerning the existence of the NLRO in the ground state of antiferromagnetic, spin-1/2 systems on two dimensional, Archimedean lattices, is formulated. 
Piotr Tomczak (1) and J.Richter (2) ((1) Adam Mickiewicz University,   Poznan, Poland; (2) University of Magdeburg, Germany)