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 liquidHe 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 of 0.4 nm. Magnetic moments of the Fe and the Ni layers have been calculated based on linear muffintin orbital method, and are significantly higher than the measured values.