Antiferromagnetic and ferromagnetic order in Co/Ru multilayers

The magnetic order of several polycrystalline cobalt-ruthenium multilayers was determined by polarized neutron reflectometry. Measurements were made on four samples comprised of nominally 30 Å thick Co layers separated by Ru layers nominally 6.6, 11, 17.6 and 22 Å thick respectively. These studies confirm that adjacent cobalt layers, in themselves ferromagnetic, couple alternatively antiferro- and ferromagnetically when the ruthenium thickness is increased. In addition, neutron scattering at grazing incidence reveals that the lateral extension of the antiferromagnetic domains is limited, and does not exceed a few thousand ångströms. In the predominantly ferromagnetically coupled multilayers evidence for a tiny portion of AF coupled regions is found. © 1991.