Nonoscillatory magnetoresistance in Co/Cu/Co layered structures with oscillatory coupling

Abstract

Using sputtered thin-film layered structures comprising Si/[8\ifmmode\times\else\texttimes\fi{}(20-\AA{} Ru/x Cu)] /(30-\AA{}) Co/${\mathit{t}}_{\mathrm{Cu}}$ Cu/30-\AA{} Co /(150-\AA{} ${\mathrm{Fe}}_{50}$${\mathrm{Mn}}_{50}$) with x=8 and 12 \AA{}, we demonstrate that the oscillation in the coupling of the two Co layers as the Cu-layer thickness, ${\mathit{t}}_{\mathrm{Cu}}$, is varied, is not accompanied by an oscillation in the amplitude of the magnetoresistance. Thus the previously reported oscillation in magnetoresistance in Fe/Cr, Co/Ru, Co/Cr, and Co/Cu multilayers is not a fundamental electronic effect but a consequence of the inability to vary consistently the angles between the magnetizations of these multilayers.