A Theory of Ferromagnetic Superconductors —An Analysis of Experiments on ErRh₄B₄ and HoMo₆S₈—

Abstract

The coexistence problem of ferromagnetism and superconductivity is discussed theoretically. Recent experiments on the rare earth ternary compounds ErRh₄B₄ and HoMo₆S₈ are analyzed on the basis of the sf exchange interaction model. It is shown that the ferromagnetic molecular field effect of the sf exchange interaction is crucial in explaining the data and the spatially inhomogenous superconducting state coexisting with ferromagnetism can describe adequately various aspects of the sinusoidally modulate magnetic structure observed in both compounds.