Propagation of magnetic and superconducting order in Gd/La superlattices

Single-crystal Gd/La superlattices have been grown by molecular beam epitaxy. The magnetic ordering has been determined using neutron scattering and the superconducting transitions have been identified using SQUID magnetometry. The Gd layers order ferromagnetically below T∼280 K and the interlayer coupling across the La layers is antiferromagnetic. Surprisingly, when cooled in zero field below T∼5 K the Gd/La superlattices exhibit 3D superconductivity, even when the thickness of the La blocks is only 13 atomic planes. The transition from the normal to the superconducting phase does not affect the magnetic structure. In contrast, field cooling results in ferromagnetic coupling of the Gd blocks and, under these conditions, the superconducting transition is suppressed