Correlation between magnetic and transport properties of Co/Ir/Co sandwiches and surface roughness

Co_{3 nm}/Ir_x/Co_{3 nm} sandwiches with 0.5, 1 and 1.5-nm thickness of Ir were deposited on glass substrates covered by a Fe_{5 nm}/Co_{0.5 nm}/Cu_{3 nm} layer, using the ion beam sputtering (IBS) technique. The maximum giant magnetoresistance and coupling strength were, respectively, 2% and −0.55 erg/cm². The magnetic and transport properties were investigated and correlated with atomic force microscopy measurements. The surface roughness was analyzed at each stage of the growth by calculating the root mean square (RMS) on surfaces of 1×1 μm². The average roughness was small, approximately 0.3 nm, which is a necessary condition to observe an anti-ferromagnetic exchange coupling in a sandwich stack.