SPECULAR REFLECTION IN SPIN VALVES BOUNDED BY NIO LAYERS

We have experimentally investigated the possibility of increased elect ron reflectivity induced by an insulating NiO layer that is used to ex change bias a metallic spin-valve. For this purpose Ni80Fe20/Cu/Ni80Fe 20 and Ni66Fe16Co18/CU/Co90Fe10 spin-valves were grown and subsequentl y covered by insulating NiO or by metallic FeMn, Zn all cases the gian t magnetoresistance of the NiO spin-valves is systematically larger up on a variation of the exchange-biased ferromagnetic layer thickness, a lso after correcting the data for the conductivity of FeMn which we ha ve determined from a separately grown series of samples with variable FeMn thickness. The increased giant magnetoresistance ratios can be qu alitatively understood on the basis of a semiclassical calculation in which (partial) specular reflectivity at the NiO interface has been in cluded.