Effects of lattice expansion and moment enhancement on saturation magnetization of Fe70Co30 sublayersin [Fe70Co30/M]n super-lattice films

We reported that the saturation magnetization (B_s(FeCo)) of Fe₇₀Co₃₀ sublayers in sputtered [Fe₇₀Co₃₀/Pd]_n super-lattice film was as high as 2.66 T, while that of Fe₇₀Co₃₀ single-layered film was 2.35 T. The high-B_s(FeCo) seemed owing to the increase of magnetic moment of Fe atoms induced by the enhancement by neighboring Pd atoms and by the magnetovolume effect due to the expansion of lattice constant of Fe₇₀Co₃₀ crystallites. The lattice expansion seemed to depend on only the atomic size of interlayer materials, so it was expected that when the materials such as Rh and Ag, which have almost same atomic size as Pd, were used as interlayer in super-lattice films, B_s(FeCo) would increase by magnetovolume effect. In this study, B_s(FeCo) in [Fe₇₀Co₃₀/M]_n (M= Rh, Pd and Rh-Pt) films with various interlayer thickness (t_int) were investigated.