Effect of microstructure on resistivity and GMR ratio in ion beam deposited spin valves

We indicate one microstructural feature which can control the GMR ratio in a series of highly (111)-textured, ion-beam deposited "top" spin valves. The textural dispersion, as measured by x-ray diffraction rocking curves, is shown quantitatively to influence the resistivity, and indirectly, the GMR ratio, producing a factor-of-three variation from 2% to 6%. Concurrent variations in the degree of antiparallel alignment are ruled out. To study more closely the dependence of resistivity on textural dispersion, the trend has been reproduced on single Cu films of comparable thickness. Fits to resistivity vs. thickness, AFM, and TEM characterization of the Cu films indicate that the resistivity variations come from spin-independent scattering in the bulk rather than at the surfaces of the films. The GMR variation is attributed to variations in the grain-boundary scattering; however, differing contributions of the grain boundary reflectivity and of the grain size could not be separated.