Enhancement of perpendicular and parallel giant magnetoresistance with thenumber of bilayers in Fe/Cr superlattices

We have correlated a detailed quantitative structural analysis by x-ray dif fraction, transmission electron microscopy, and high spatial resolution ele ctron energy-loss spectroscopy imaging, with the magnetization and anisotro pic magnetotransport properties in sputtered Fe/Cr superlattices. To accomp lish this, we developed a technique for magnetotransport measurements in me tallic superlattices with the current perpendicular to the plane of the lay ers (CPP). Using microfabrication techniques, we have fabricated microstruc tured Fe/Cr pillars embedded in SiO2 and interconnected with Nb electrodes. Because of the uniform current distribution in the Nh electrodes and the m inimization of the superlattice-electrode contact resistance, the method al lows a simple and independent measurement of the superlattice resistance an d giant magnetoresistance (GMR). Structural and magnetic characterization o f [Fe(3 nm)/Cr (1.2 nm)](N) superlattices (where N is the number of repetit ions) indicate that the roughness is correlated and increases cumulatively through the superlattice stack with no significant change in the antiferrom agnetic coupling. Both the current in-plane and CPP GMR increase with N as the roughness increases.