Dependence of the dielectric function and electronic properties on the Co layer thickness in giant-magnetoresistance Co/Au multilayers

A series of Co/Au multilayers, which exhibit (111) texture and low-field giant magnetoresistance (GMR), were examined with spectroscopic ellipsometry (SE) in a range of Co layer thicknesses (t(Co)) The obtained optical dielectric functions show a systematic variation with increasing t(Co). Analysis of the optical transitions reveals nonmonotonic variations in plasma frequency omega(p) and the interband parameters with increasing t(Co). These anomalies in the electronic states reflect drastic changes in Co layering above 1.5 nm of t(Co) The complementary study of SE and GMR measurements, on similar Co/Cu and Co/Au multilayers with (111) texture, provide experimental evidence that an interplay between spin-dependent interface and bulk scattering contributions can explain the observed linear decrease of GMR with increasing t(Co). [S0163-1829(99)06341-9].