Effect of annealing on the giant magnetoresistance of sputtered Co/Cu multilayers

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Abstract
Co/Cu multilayers with the form of glass/Cu 50 Å[Co11.5 Å/Cu(tCu)]30/Cu50 Å, prepared by rf triode sputtering, exhibit oscillatory magnetoresistance (MR), as a function of the Cu layer thickness with a period of ≂12 Å and maximum MR values of 36.8% and 22.3% at 77 and 295 K, respectively. In order to study the effect of annealing on the structural and magnetic properties, five samples with Cu thicknesses between 9 and 34 Å were heat treated at temperatures up to 300 °C and analyzed by low‐ and high‐angle x‐ray diffraction, MR, and mageto‐optic Kerr effect measurements. Annealing at moderate temperatures for the samples with Cu thicknesses around the second and third MR peaks leads to an initial increase in the MR. In contrast, annealing causes only a monotonic MR decrease for the sample at the first peak with a Cu thickness of 9 Å.