Induced magnetic anisotropy, stress and hysteresis in FeCoV/TiNx multilayers

FeCoV/TiN_x supermirrors that are composed of multilayers with graded thickness are used for the polarization of cold neutrons. In this paper, the investigations on the thickness dependence of the magnetic properties of FeCoV/TiN_x multilayers prepared by DC magnetron sputtering are described. Moving the substrates during the sputtering process leads to an in-plane easy axis of magnetization. The easy axis arises due to the presence of stress anisotropy which in turn induces a magnetic anisotropy through magnetostrictive effects. The stress measurements show that the difference between the stress perpendicular and parallel to the substrate movement is almost independent of the thickness of the FeCoV layers. In-plane magnetic hysteresis data display a remanent magnetization of about 95% for all the samples. The data also show a linear increase of coercivity with increasing thickness of the magnetic FeCoV layers. The linear increase is related to the increase in grain size with increasing thickness of the layers