Superconducting ferromagnets: Ferromagnetic domains in the superconducting state

The conditions under which superconductivity and ferromagnetism can exist simultaneously in magnetic materials, are discussed. Ferromagnetic state with a spiral or a domain-like non-uniform structure can coexist with a with superconducting state. Superconductivity arising in a ferromagnetic multidomain state causes a dramatic shrinkage of the domain size. It has been observed that the vortex density increases with the intensity of the magnetic field. In the case of superconducting ferromagnets, the superconducting order parameter seems to have a similar effect on the ferromagnetic domain state, increasing the domain density by shrinking the domain width.