Achieving uniaxial magnetic anisotropy in Ce 2 Fe 17 N 3 through Co- and Sm-substitution

${\mathrm{Th}}_{2}{\mathrm{Zn}}_{17}\text{\ensuremath{-}}\mathrm{type}$ structure-based permanent magnets, such as ${\mathrm{Sm}}_{2}{\mathrm{Fe}}_{17}{\mathrm{N}}_{3}$, offer strong potential as alternatives to neodymium magnets (NdFeB), but their practical use is limited by phase stability and the scarcity of Sm. Ce-based counterparts, particularly ${\mathrm{Ce}}_{2}{\mathrm{Fe}}_{17}{\mathrm{N}}_{3}$, are attractive low-cost candidates, yet their intrinsic planar magnetic anisotropy restricts permanent-magnet performance. Here, we induce uniaxial magnetic anisotropy in ${\mathrm{Ce}}_{2}{\mathrm{Fe}}_{17}{\mathrm{N}}_{3}$ through two approaches: (i) Co substitution on the Fe sublattice and (ii) partial substitution of Ce with Sm. Combined density functional theory and experimental results show that both strategies modify the $3d\text{--}4f$ interactions and band filling, yielding magnetization values up to $\ensuremath{\sim}1.2\phantom{\rule{0.28em}{0ex}}\mathrm{T}$ and magnetocrystalline anisotropy energies exceeding $1\phantom{\rule{0.28em}{0ex}}\mathrm{MJ}/{\mathrm{m}}^{3}$ for Co-alloyed compositions, with significantly larger anisotropy achieved upon Sm substitution. In addition, the Sm-substituted ${\mathrm{Ce}}_{2}{\mathrm{Fe}}_{17}{\mathrm{N}}_{3}$ samples exhibit enhanced high-temperature stability compared to ${\mathrm{Sm}}_{2}{\mathrm{Fe}}_{17}{\mathrm{N}}_{3}$. These findings demonstrate that ${\mathrm{Ce}}_{2}{\mathrm{Fe}}_{17}{\mathrm{N}}_{3}$-based alloys can deliver magnetic performance suitable for permanent-magnet applications while reducing cost and reliance on critical rare-earth elements, and they provide practical design guidelines for rare-earth-lean magnets for energy and industrial applications.