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We study systems of classical magnetic dipoles on simple cubic lattices with dipolar and antiferromagnetic exchange interactions. By analysis and Monte Carlo (MC) simulations, we find how the antiferromagnetic phases vary with uniaxial and fourfold anisotropy constants, C and D, as well as with exchange strength J. We pay special attention to the spin reorientation (SR) phase, and exhibit in detail the nature of its broken symmetries. By mean field theory and by MC, we also obtain the ratio of the higher ordering temperature to the SR transition temperature, and show that it depends mainly on D/C, and rather weakly on J. We find a reverse SR transition.
We study classical and quantum Heisenberg antiferromagnets with exchange anisotropy of XXZ-type and crystal field single-ion terms of quadratic and cubic form in a field. The magnets display a variety of phases, including the spin-flop (or, in the qu
Classical anisotropic XY antiferromagnets in a field on square and simple cubic lattices are studied using mainly Monte Carlo simulations. While in two dimensions the ordered antiferromagnetic and spin--flop phases are observed to be separated by a n
We use numerical transfer-matrix methods, together with finite-size scaling and conformal invariance concepts, to discuss critical properties of two-dimensional honeycomb-lattice Ising spin-1/2 magnets, with couplings which are antiferromagnetic alon
We simulate antiferromagnetic thin films. Dipole-dipole and antiferromagnetic exchange interactions as well as uniaxial and quadrupolar anisotropies are taken into account. Various phases unfold as the corresponding parameters, J, D and C, as well as
This paper has been withdrawn by the authors due to a possible inconsistency in the program code.