Saturation magnetization of ultra-thin Ni-20 at%Fe layers in Ni-Fe/Cu multilayers

Abstract

Saturation magnetizations in Ni–20 at% Fe/Cu multilayers with Ni–Fe layers of 0.2–2.0 nm in thickness have been investigated experimentally and theoretically. The saturation magnetization 4π M s of the Ni–Fe layers was around 10 kG at room temperature, when the thickness of the Ni–Fe layers was above 1.6 nm. Below 1.6 nm, the 4π M s decreased as the thickness decreased, and became 0 kG at 0.2–0.3 nm. The 4π M s at liquid-He temperature also decreased with decreasing thickness below 1.6 nm. However, the 4π M s was relatively high even at 0.5–0.6 nm, and low but not 0 kG at 0.2–0.3 nm, compared with the 4π M s at room temperature. Magnetic moments of the Ni–Fe layers have been calculated based on linear muffin-tin orbital method, and were significantly higher than the measured values at liquid-He temperature.