QUANTITATIVE INTERPRETATION OF GIANT MAGNETORESISTANCE PROPERTIES OF PERMALLOY-BASED SPIN-VALVE STRUCTURES

We analyse quantitatively the low-temperature magnetotransport properties of a series of spin-valve structures of composition NiFe t angstrom/Cu 22 angstrom/NiFe 50 angstrom/FeMn 80 angstrom/Cu 15 angstrom. We adopt the approach of Camley and Barnas which is based on the classical Boltzmann equation and assume spin-dependent scattering in the bulk of the ferromagnetic layers. We show that by introducing an anisotropy in the mean-free paths of conduction electrons (of the order of 30%) we can fit with the same set of parameters the variation of the sheet conductance and magnetoresistance with the thicknesses of the Cu and NiFe layers. This anisotropy is ascribed to grain boundaries scattering in these sputtered polycrystalline samples. We also compare our results with others obtained on (Fe/Cr)-type spin-valve multilayers. We emphasise the very important role of the number of periods of the multilayered structure on the magnetotransport properties of these systems.