CoFe/IrMn spin-valves prepared on Cu islands

By inserting only a 0.75 nm-thick Cu layer between the CoFe/Cu/CoFe/IrMn spin-valve stack and Ta underlayer, the magnetoresistance (MR) ratio and /spl Delta/R were about 1.8 and 1.4 times, respectively, as large as those without the Cu layer. Atomic force microscopy, X-ray diffraction, and MR measurements suggest that the Cu "islands" formed in the initial growth stage modified the interfaces of the spin-valve and the structure of the component layers, resulting in the enhancement of the spin-dependent electron scattering. When the inserting Cu thickness (t) was larger than 1.5 nm, not only the MR characteristics but the magnetic properties, such as coercivity of the free layer, was improved in comparison with that of t=0 nm. This is due to the considerable increase in the crystallinity of the spin-valve films. In this thickness range, Cu is expected to function as the buffer "layer".