ANTIFERROMAGNETIC INTERLAYER CORRELATIONS IN ANNEALED NI80FE20 AG MULTILAYERS/

Sputtered Ni80Fe20/Ag multilayers, annealed post-growth, exhibit giant magnetoresistance (GMR) with pronounced field sensitivity [T. L. Hylt on et al., Science 261, 1021 (1993)], We have characterized a series o f Ni80Fe20(20 Angstrom)/Ag(40 Angstrom) multilayers annealed at temper atures ranging from 305 to 335 degrees C using x-ray and polarized neu tron reflectivity techniques. For all of the samples, specular x-ray m easurements reveal that the laterally averaged interfaces between the Ni80Fe20 and Ag layers are not well defined. The growth-plane morpholo gy of the multilayers, determined from off-specular x-ray diffraction, shows a dependence on annealing temperature. Specular and off-specula r polarized neutron reflectivity data indicate that the GMR in the ann ealed samples does not arise from long-range antiferromagnetic alignme nt of coherent ferromagnetic sheets, as generally observed in related materials. Instead, annealing promotes the formation of planar ferroma gnetic domains of micrometer size within each Ni80Fe20 layer that are antiferromagnetically correlated along the growth axis. The length sca les of these domains are consistent with a model in which weak dipolar forces dominate the interactions between them.