Effects of annealing on the magnetoresistance and structure of Fe/Cr(110) superlattices

We have performed magnetotransport, magnetization, and structural experiments on sputtered Fe(30 Angstrom)/Cr(12 Angstrom) (110) superlattices that were annealed at temperatures up to 400 degrees C. Interestingly, their giant magnetoresistance (Delta rho) is enhanced at intermediate temperatures, and strongly decreased at higher temperatures. If normalized to the antiferromagnetic coupling fraction of sample, the magnetoresistance increases over the entire annealing range. From low-angle x-ray-diffraction measurements, the enhancement of Delta rho arises from an interface redistribution because of either a slight interdiffusion, less correlated interfaces, or both. Further annealing causes extreme interdiffusion that is detrimental for the magnetoresistance because of a loss of antiferromagnetic coupling.