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 Nd
₂
Fe
₁₄
B (512 kJ/m
³
) or SmCo
₅
(230 kJ/m
³
). 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/m
³
, i.e., significantly above the theoretical hard phase limit of SmCo
₅
, have been realized in fully epitaxial SmCo
₅
/Fe/SmCo
₅
trilayers. Here we extend our work to fully epitaxial SmCo
₅
/Fe multilayers with reduced individual layer thicknesses of Fe and SmCo
₅
. 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/m
³
. 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.