Fully Epitaxial, Exchange Coupled SmCo$_{5}$/Fe Multilayers With Energy Densities above 400 kJ/m $^{3}$

Exchange coupled hard/soft magnetic nanocomposites have long been in the interest of research for improving the energy density of the currently best hard magnetic materials such as Nd₂ Fe₁₄B (512 kJ/m³) or SmCo₅ (230 kJ/m³). However, to compete with the energy density of a well textured single phase bulk magnet, the hard magnetic phase within the two-phase material should be sufficiently textured as well. Thus, only recently values of more than 300 kJ/m³, i.e., significantly above the theoretical hard phase limit of SmCo₅, have been realized in fully epitaxial SmCo₅/Fe/SmCo₅ trilayers. Here we extend our work to fully epitaxial SmCo₅ /Fe multilayers with reduced individual layer thicknesses of Fe and SmCo₅. The rigid coupling of a large volume fraction of high moment soft phase to a hard magnetic Sm-Co phase leads to energy densities above 400 kJ/m³. Phase formation, epitaxial texture and magnetic properties are discussed for a series of multilayers of constant total thickness with respect to the number of introduced interfaces.