Giant magnetoresistance and antiferromagnetically coupled Co fraction in Co/Cu multilayers with varying number of periods

摘要

The giant magnetoresistive signal of Co/Cu multilayers as a function of the number N/sub Co/ of Co layers is experimentally investigated for Cu thicknesses of 1 nm, i.e. in the 1st antiferromagnetic maximum, and for Co layer thickness of 1 nm. The stacks were deposited by DC magnetron sputtering on an Fe buffer. The fraction F/sub AF/ of the film that couples antiferromagnetically is derived from the hysteresis curves. A correction of F/sub AF/ is required for the buffer and one Co layer. The F/sub AF/ of stack periods close to the buffer is about 1, while F/sub AF/ reduces at large stack thicknesses. The GMR of stacks with small thicknesses is limited by the diffuse scattering at the outer surfaces. The GMR of thicker stacks depends on F/sub AF/ and the resistivity. Furthermore, the meaning of F/sub AF/ is discussed. By optimizing N/sub Co/, we achieved /spl Delta//spl rho///spl rho/'s as high as 72% at room temperature.