Competing magnetic anisotropies in exchange coupled bilayers with growth-induced orthogonal uniaxial axes

Magnetic anisotropy has been studied in YCo2/YCo2 amorphous bilayers with variable thickness and orthogonal in-plane uniaxial anisotropies of the individual layers induced in the sputtering growth. The study of the magnetization reversal and the effective magnetic anisotropy of the bilayers has been performed as a function of the relative strength of the competing individual-layer anisotropies by magneto-optical measurements and transverse bias initial susceptibility measurements. Analysis of the results on the basis of an analytical phenomenological model and micromagnetic simulations allows the interpretation of the observed behaviors; it reveals the presence of a region at the interface with a strongly reduced anisotropy as well as a nonmonotonic variation of the global effective anisotropy of the bilayer as a function of the top layer thickness.