Co/Cu系多層膜の積層回数とそのMR特性及び磁気特性  [in Japanese] Dependence of the Number of Bilayers (Co/Cu) on the Magnetoresistance and Magnetic Characteristics of (Co/Cu) Multilayer Systems  [in Japanese]

The magnetoresistance and magnetic characteristics of (Co/Cu)_N/Co and (Co/Cu)_N/Co/IrMn multilayer systems were investigated in terms of the number of bilayers (Co/Cu). In a (Co/Cu)_N/Co system, no interaction was found among Co layers for N≦3, but weak antiferromagnetic interaction emerged for N=4 and increased for N≧5. In a (Co/Cu)_N/Co/IrMn system, a uniaxial exchange-coupling field was found for N≦2, spin-valve like interaction emerged for N=3,4 and antiferromagnetic interaction was dominant for N≧5. Antiferromagnetic coupling energies were estimated from magnetization loops and were found to increase as the number of bilayers N increased, reaching 0.0078erg/cm^2 for N=10. These values were independent of the presence of an IrMn layer, and this fact proved that owing to weak interaction between the top Co layer and the inner Co layer, no antigerromagnetic domain reorientation occurred when the top Co layer was unidirectionally pinned by IrMn.