Magnetic properties versus interface density in rigid-exchange-coupled amorphous multilayers with induced uniaxial anisotropy

Abstract

We demonstrate the possibility to tune the saturation magnetization, coercivity, and uniaxial in-plane anisotropy constant in amorphous bilayers and multilayers of Co85(Al70Zr30)15 and Sm11Co82Ti7 through the interface density. From magnetometry and x-ray circular dichroism (XMCD) measurements, we conclude that the easy-axis coercivity μ0Hc increases four times when the number of bilayer repetitions, N, increases from 1 to 10 within a constant total sample thickness of 20 nm. At the same time, the anisotropy constant Ku also increases by a factor four, whereas the saturation magnetization Ms decreases slightly. The Co spin and orbital moments, ms and ml, are found to be approximately constant within the sample series. The average total Co moment is only 0.8–0.9 μB/atom, but the ml/ms ratio is strongly enhanced compared to pure Co. Magnetization curves extracted from XMCD measurements show that the Co and Sm moments are ferromagnetically coupled for all samples.