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On the coexistence of superconductivity and itinerant ferromagnetism
Author(s) -
Kolley E.,
Kolley W.
Publication year - 1982
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.2221140116
Subject(s) - condensed matter physics , ferromagnetism , superconductivity , physics , quartic function , hubbard model , formalism (music) , quadratic equation , mean field theory , percolation (cognitive psychology) , percolation threshold , electron , quantum mechanics , mathematics , electrical resistivity and conductivity , art , musical , neuroscience , visual arts , biology , geometry , pure mathematics
The interplay of superconductivity and ferromagnetism in an itinerant electron system is described by attractive contact and repulsive Hubbard interactions within a substitutionally disordered tight‐binding model. Functional integral formalism at nonzero temperatures is employed in going over from Grassmann variables to collective Bose fields to derive microscopically the quadratic and quartic terms in the loop expansion of the effective action. The configurational averaging is performed on the mean field level to find out a Landau‐type theory for two biquadratically coupled coherent order parameters. It is proved that the coexistence region for the superconducting and ferromagnetic phases cannot be reached in the percolation limit of A x B 1– x alloys. For testing the present method the results of the itinerant and localized spin models are compared.