MAGNETISM AND EPITAXY IN LU/DY/LU TRILAYERS

Thin dysprosium c-axis films (40-400 angstrom) were grown coherently between 500-angstrom lutetium layers by molecular beam epitaxy. Bulk magnetization measurements show that these sandwich structures order magnetically at T(N) congruent-to 178 K (= T(N) of elemental Dy) and undergo ferromagnetic transitions at temperatures which range from 100 K (400 angstrom Dy) to 175 K (40 angstrom Dy), significantly enhanced from the bulk T(C) = 85 K. The Dy basal plane lattice parameters in the films were determined by room-temperature x-ray diffraction. We observe a change in these values that correlates with the rise in T(C), which suggests that this rise is due to epitaxial strain. The relatively small low-temperature magnetic susceptibility displayed by these samples indicates the presence of a large anisotropy in the basal plane. We address both the issues of the susceptibility and the high ferromagnetic transition temperature.