Journal of Physical Studies 1(3), 301–313 (1997) DOI: https://doi.org/10.30970/jps.01.301 COMPREHENSIVE ANALYSIS OF MAGNETIC SUPERSTRUCTURES IN ANISOTROPIC SYSTEMS

N. Gonchar^*, W. Kozyrski^**, H. Hajduk
Department of Mathematical Modelling, N. Bogolubov Institute for Theoretical Physics,
Ukrainian National Academy of Sciences, 14b Metrolohichna Str., Kyiv UA-252143, Ukraine
^*E-mail: mgonchar@gluk.apc.org, ^**E-mail: kozyrski@gluk.apc.org

New method is developed for analytical treatment of mo\-dulated superstructures in model magnetic systems near criticality. We found the conditions for paramagnet-(in)commensurate transition in the class of anisotropic Ising models with and without an external magnetic field and the critical value of the latter. We derived a new representation of specific free energy for commensurate and incommensurate configurations and found its hidden symmetry. The existence of the global solution is proved for the incommensurate configuration minimizing free energy. We found the condition for the global solution's termination. The existence of phase transition from the incommensurate phase into the ferromagnetic one is proved to depend on exchange integrals.

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