STRUCTURE AND MAGNETISM OF DYSPROSIUM ZIRCONIUM MULTILAYERS

Dy/Zr bilayers and multilayers were grown on oxydized Si(100) substrat es by evaporation under ultrahigh vacuum conditions. X-ray and electro n diffraction shows that both Zr and Dy layers are hexagonal, strongly textured with the c-axis along the growth direction. The grains can e xtend over several layers and have an in-plane diameter of about 200 A ngstrom. The Dy lattice displays an in-plane compression of about 1.5% . Interface profiles determined from high-resolution electron microsco py studies are sharp, extending over less than 3 lattice spacings, Mag netization measurements and polarized neutron reflectometry reveal a s trong enhancement of T-C, accompanied with a suppression of the helica l antiferromagnetic phase in the multilayer samples. This effect can b e understood as the result of the change in the balance between exchan ge and magnetoelastic energies caused by in-plane epitaxial compressio n of the Dy lattice by Zr. A large out-of-plane magnetic anisotropy en ergy is observed when the Dy layers are made thinner than 15 Angstrom. Volume and interface contributions to this anisotropy compensate each other for a Dy layer thickness of about 8 Angstrom. Comparison is mad e between the results of crystal-field calculations based on the point -charge approximation and the measured anisotropy energy.