Saturation magnetization of ultra-thin Fe and Ni layers in (Fe,Ni)/Cu multilayers

We have experimentally and theoretically investigated saturation magnetizations of Fe layers and Ni layers with thicknesses of 0.2-2.0 nm in Fe/Cu and Ni/Cu multilayers. The saturation magnetizations 4πM_S of the Fe layers at room temperature and at liquid-He temperature are 21 kG at the thicknesses above 1.4 nm, and decrease with decreasing thickness below 1.4 nm. The 4πM_S of the Fe layers at liquid-He temperature and at room temperature are 8 kG and 3 kG, respectively, when the thickness of the Fe layers is 0.2 nm (1 ML). The 4πM_S of the Ni layers at room temperature and at liquid-He temperature are 5-6 kG at the thickness of 2.0 nm, also decrease with decreasing thickness below 1.6 nm, and become 0 kG at 0.2 nm (1 ML). The observation of the cross-section of the Fe/Cu multilayers indicates that the Fe layers are continuous and flat, even though the thickness of the Fe layers is ultra-thin (0.4 nm). Magnetic moments of the Fe and the Ni layers have been calculated based on the linear muffin-tin orbital method, and are significantly higher than the measured values