Microstructure and magnetic properties of Co/Os/Co and Fe/Os/Fe thin films

The Co/Os/Co and Fe/Os/Fe thin films were deposited on natural oxidized Si (1 0 0) substrates at room temperature by magnetron sputtering. The thickness was kept at 100 Å for all the magnetic layers, and was varied between 3 and 20 Å for the Os layer. Effects of the Os layer thickness and microstructure on the magnetic properties of the film were investigated. The results showed that the antiferromagnetic coupling occurred for the Co/Os/Co thin films with the Os thickness between 7 and 13 Å. Due to the mismatch of Fe and Os, pinholes in the Os layer could be observed. The presence of interface roughness and pinholes reduces the antiferromagnetic interlayer exchange coupling strength and affect the dependence of the interlayer exchange coupling on the Os layer thickness. From the magnetoresistance (ΔMR) study, the largest ΔMR ratio arising from antiferromagnetic coupling for Co/Os/Co and Fe/Os/Fe thin films are about 0.45% and 0.07% respectively. The small ΔMR in Fe/Os/Fe system is explained by the large interface roughness and lattice mismatch effect.