Magnetic structures and coherence of rare earth superlattices

Abstract

Neutron and X-ray scattering techniques have been used to characterise and study the rare earth superlattices and the superlattices of Laves phase materials. For the rare earth superlattices systems such as Ho/Y, Ho/Lu, Dy/Y and Ho/Dy have magnetic structures with coherence over hundreds of angstroms. In contrast other systems such as Ho/Pr, or Ho/Sc or Ho/Er do not have long-range coherence. It is argued that this is because the conduction electrons can cross the interfaces easily in the first group of materials but that in the second they cannot due to different Fermi surfaces, different lattice constants or different magnetic structures. The Laves phase systems are ferromagnets but with the rare earth materials polarised oppositely to the 3d transition metals. The phase diagram is then complex and depends both on the relative and absolute thickness of the constituents.