CoFe/Ir/CoFe artificial antiferromagnetic sandwich as a hard magnetic layer in hard-soft GMR sensors

We report on the magnetic and transport properties of CoFe3 nm/Ir-0.5 nm/Co Fe3 nm and CoFe1.5 nm/Ir-0.5 nm/CoFe3 nm sandwiches, grown by ion beam sput tering. The sandwich with identical CoFe thicknesses presents a small rigid ity and no plateau around zero field. For the same coupling strength, this rigidity and the plateau are strongly improved for the sandwich with asymme trical CoFe thicknesses. In both cases, when the thicker layer is on the to p or on the bottom of the AAF, coercive fields H-C of 600 Oe are obtained. However, the GiNIR plateau is only slightly improved for asymmetric sandwic hes, probably due to lateral coupling fluctuations. Roughness analysis and TEM observations have been made in order to confirm the last hypothesis.