Abstract:
We use the self-consistent harmonic approximation (SCHA) to study the two-dimensional classical Heisenberg anisotropic (easy-plane) ferromagnetic model including nearest- and next-nearest neighbor exchange interactions. For temperatures much lower than the Kosterlitz-Thouless phase transition temperature T KT, spin waves must be the most relevant excitations in the system and the SCHA must account for its behavior. However, for temperatures near T KT, we should expect vortex pairs to be quite important. The effect of these vortex excitations on the phase transition temperature is included in our theory as a renormalization of the exchange interactions. Then, combining the SCHA theory to the renormalization effect due to vortex pairs, we calculate the dependence of T KT as a function of the easy-plane anisotropies and exchange interactions.
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Received 3 April 2001 and Received in final form 20 September 2001
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Gouvêa, M., Pires, A. The two dimensional classical anisotropic Heisenberg ferromagnetic model with nearest- and next-nearest neighbor interactions. Eur. Phys. J. B 25, 147–153 (2002). https://doi.org/10.1140/epjb/e20020017
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DOI: https://doi.org/10.1140/epjb/e20020017