Magnetic superlattices fabricated by monoatomic layer control

Co/Ru superlattices were prepared by monoatomic layer control through the u se of molecular beam epitaxy technique. The Co and Ru thicknesses were vari ed in the range from 1 to 5 ML (ML: monoatomic layer thickness). Coherent l ayered structures have been confirmed for all the samples by X-ray diffract ion. For the Co and Ru thicknesses equal to I ML, furthermore, transmission electron microscopy observation shows the formation of an ordered structur e with hcp stacking of Cc and Ru atomic planes. The magnetization measureme nts indicate that the effect of direct ferromagnetic contact between Co lay ers due to bridges is negligible even when the Ru thickness is reduced to 2 ML. Only I ML difference in the Co and Ru thicknesses has strong influence on the indirect exchange coupling of Co through Ru. First-principles calcu lations support the fact that the difference in Ru thickness critically aff ects the indirect exchange coupling. (C) 2001 Elsevier Science B.V. All rig hts reserved.