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Molecular Field Theory and Landau‐Ginzburg Theory of Phase Transitions in Disordered Ferromagnets
Author(s) -
Fähnle M.
Publication year - 1980
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2220990213
Subject(s) - homogeneous , landau theory , condensed matter physics , ferromagnetism , ginzburg–landau theory , field theory (psychology) , phase transition , physics , equivalence (formal languages) , field (mathematics) , statistical physics , quantum mechanics , mathematical physics , mathematics , superconductivity , pure mathematics
The equivalence is demonstrated of molecular field theory and Landau‐Ginzburg theory for the description of the ferromagnetic phase transition. In analogy to the original (inhomogeneous) molecular field theory of disordered materials and its homogeneous version ( S j z= S z in the expression for the molecular field) an inhomogeneous and a homogeneous version of the Landau‐Ginzburg theory are derived. Within the framework of the local versions of these theories the influence of statistically random structure fluctuations on the critical temperature, T c , is investigated. It is shown that T c is either unchanged (homogeneous theory) or increased (inhomogeneous theory) in comparison to a corresponding homogeneous system, if correlations between site disorder and bond disorder are neglected. A possible way is described to decide which version of the theory is more appropriate for the description of the phase transition in disordered materials.