Low-field magnetoresistance of Fe/Cr multilayers

Sputtered {Fe/Cr} multilayers with a fixed Cr individual layer thickness t(Cr) = 2 ran and variable Fe individual layer thickness (1 mn less than or equal to t(Fe) less than or equal to 6 nm) are investigated by means of X-ray diffraction, magnetoresistance and magnetisation measurements. At room temperature, the initial magnetoresistive susceptibility of the as-deposited samples is almost constant. However, the saturation field increases with decreasing Fe-layer thickness, therefore, a maximal magnetoresistance ratio DeltaR/R of 0.7% is reached in the sample with t(Fe) = 1 nm. After annealing at 350degreesC, a DeltaR/R value as large as 2.3% was obtained. Further annealing causes a reduction of magnetoresistance. As the temperature is decreased, the DeltaR/R ratio measured in mu(0)H = 0.3 T increases linearly. At 77 K, the magnetoresistance ratio is about four times larger than that at 300 K. Results are discussed in terms of the scattering located at interfaces and the formation of a ferromagnetic state at high-temperature heat treatments. (C) 2002 Elsevier Science B.V. All rights reserved.