A series of Co/Pd superlattices with constant Pd layer thickness of d(Pd) = 11 angstrom were grown on single-crystal GaAs(110) substrates by molecular beam epitaxy (MBE). A buffer layer of 500 angstrom of Pd provided an atomically smooth, fcc(111) single-crystal starting surface for the superlattice deposition. The resulting superlattices maintain this crystal symmetry and smoothness throughout their epitaxial growth. Details of the structural characterization of these samples are given elsewhere in these proceedings. The magnetic properties of these films have been measured by vibrating sample magnetometry. A perpendicular easy axis is found for all seven of the superlattices presented (d(Co) = 2, 4, 8, 10, 12, 17, and 20 angstrom). An unusually high coercive field of H(c) = 6.6 kOe is observed for d(Co) = 2 angstrom, and decreases monotonically with increasing d(Co). The saturation magnetization agrees well with a model composed of bulk Co layers with an additional contribution from polarized Pd. The uniaxial magnetic anisotropy energy can be described by both an interface term and a large volume term favoring a perpendicular easy axis for d(Co) < 23 angstrom. Comparisons with a series of polycrystalline multilayers simultaneously deposited on Si substrates reveal significant differences in the magnetic behavior.
