Cooperative response of magnetism and superconductivity in the magnetic superconductor RbEuFe4As4

A friendly coexistence of superconductivity and magnetism is quite an unusual physical phenomenon. However, the authors find that in the new high-T${}_c$ magnetic superconductor RbEuFe${}₄$As${}₄$ the magnetic and superconducting subsystems show a remarkable cooperative response. In the external magnetic field, the magnetic Eu sublattice acts as an internal pump of the magnetic flux, while the superconducting component works as a valve controlling the flux entry through the pinning of flux-carrying Abrikosov vortices and establishes the self-organized critical state.