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 $N_{\mathrm{Gd}}$ ferromagnetic atomic planes of Gd followed by $N_{\mathrm{Y}}$ planes of nonmagnetic Y, for $N_{\mathrm{Y}}=N_{\mathrm{Gd}}=10\mathrm{}$ but not for $N_{\mathrm{Y}}=6\mathrm{} or 20$. This oscillatory behavior is consistent with recent theoretical speculation that the Gd moments are coupled through the intervening Y via the Ruderman-Kittel-Kasuya-Yosida interaction.