Ginsburg-Landau theory of two antagonistic order parameters: magnetism and superconductivity

An attempt is made to construct a Ginsburg-Landau theory of so-called magnetic superconductors. Two order parameters, the magnetization field and the gap function, are introduced in such a way as to inhibit each others growth. It is found that the non-local character of the superconducting order parameter must be taken into account in any evaluation of effects of the critical magnetic fluctuations. Some predictions are made within the limits of Ornstein-Zoernicke-like fluctuation theory and some comparison is made with available data. (Auth.)