Magnetism and epitaxy in Lu/Dy/Lu trilayers

Abstract

Thin dysprosium c-axis films (40–400 Å) were grown coherently between 500-Å lutetium layers by molecular beam epitaxy. Bulk magnetization measurements show that these sandwich structures order magnetically at TN≂178 K (=TN of elemental Dy) and undergo ferromagnetic transitions at temperatures which range from 100 K (400 Å Dy) to 175 K (40 Å Dy), significantly enhanced from the bulk TC=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 TC, 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.