Revisiting Seed Thickness: When Improved Texture Does Not Enhance Perpendicular Magnetic Anisotropy in Co/Pt Multilayers

We investigated the impact of the Pt seed layer thickness on the magnetic properties of [Co(0.4 nm)/Pt(0.7 nm)]25multilayers (MLs) when using a Ta adhesion layer on an amorphous SiO2substrate. Using magnetometry, X-ray diffraction, and X-ray reflectivity, we quantitatively correlated the perpendicular magnetic anisotropy (PMA) with the seed roughness and MLs texture by fitting the X-ray reflectivity and defining a self-defined texture parameter, respectively. We find that, above a certain threshold, seed roughness and ML texture are correlated and increase with the seed’s thickness. Magnetically, we observe only small changes in PMA that are anticorrelated with the seed’s roughness, effectively reducing PMA at higher seed thicknesses despite improved texture. We propose a competition between detrimental roughness increases that reduce interfacial anisotropy and beneficial texture improvements that increase magnetocrystalline anisotropy, which we validate by comparing to previous results. For Co/Pt MLs with very thin individual layers, we conclude that the underlayer roughness has a much stronger impact on the system’s PMA than the crystal quality, marking another important factor in tuning the magnetism of such MLs.