Magnetic properties of Co/Pd multilayers determined by Brillouin light scattering and SQUID magnetometry

Abstract

Co/Pd multilayers with modulation wavelengths between 4 and 220 Å have been prepared by magnetically enhanced dc-triode sputtering on single-crystal sapphire substrates. Their saturation magnetization and volume and interface anisotropies have been investigated using Brillouin light scattering from collective spin waves and by SQUID magnetometry. The saturation magnetization of Co is found to be independent of the Co layer thickness and reduced by about 20% from the Co bulk value. From the comparison of the results of the two experimental methods, clear evidence for a Pd polarization is found and the polarization depth is estimated. Samples with Co thicknesses of 2 atomic layers and Pd thicknesses ≥5 atomic layers exhibit a perpendicular magnetization due to a large negative out-of-plane interface anisotropy. The properties of spin waves in Co/Pd multilayers with the direction of magnetization pointing out-of-plane are discussed with respect to an appropriate theoretical model.