Observation of a magnetic antiphase domain structure with long- range order in a synthetic Gd-y superlattice.

A microscopic magnetic antiphase domain structure has been observed in a single-crystal Gd-Y superlattice by neutron diffraction. Furthermore, this long-range antiferromagnetic correlation is found to occur in a multibilayer in which each bilayer consists of N(Gd) ferromagnetic atomic planes of Gd followed by N(Y) planes of nonmagnetic Y for N(Y) = N(Gd) = 10 but not for N(Y) = 6 or 20. This oscillatory behavior is consistent with recent theoretical speculation that the Gd moments are coupled through the intervening Y via the RKKY interaction.