Magnetic nesting and coexistence of ferromagnetism and superconductivity

If the condition ε_σ(p)=ε_−σ(−p+n I/v _F) for magnetic nesting is fulfilled for the electron dispersion law with spin σ along a certain preferential direction n, ferromagnetism and the inhomogeneous superconducting state can coexist up to a very high magnetization I. This fact was used to explain the coexistence of ferromagnetism and superconductivity for layered cuprates of the RuSr₂GdCu₂O₈ type, which possess a finite, though rather high, critical magnetization, because the conditions for magnetic nesting are fulfilled only approximately.