Morphological, Magnetic, and Microstructural Study of Fe/Co Multilayers Grown at Different Temperatures

Co/Fe multilayers were grown onto different substrates by means of a molecular beam epitaxy system equipped with e-guns. The microstructural and magnetic properties were studied as a function of both the growing temperature and the Fe-layer thickness. All the samples grown at room temperature show a magnetic behavior typical of systems having a strong uniaxial in-plane anisotropy. The Fe-layer thickness influences the strength of the in-plane anisotropy. By growing the samples at high temperature, a reduction of the Fe/Co intermixing occurs and the magnetic behavior becomes strongly influenced by the nature and crystallinity of the substrates. In particular, using glass substrates, the in-plane uniaxial anisotropy strengthens, whereas when using MgO monocrystalline substrates, a second in-plane easy magnetization axis establishes perpendicular to the main one. Using naturally oxidized Si substrates, a significant out-of-plane contribution to the anisotropy appears, giving rise to a magnetic behavior controlled by the competition between the perpendicular anisotropy and the demagnetizing field.