${\mathrm{Th}}_2{\mathrm{Zn}}_{17}\text{−}\mathrm{type}$ 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 $\sim 1.2\mathrm{T}$ and magnetocrystalline anisotropy energies exceeding $1\mathrm{MJ}/{\mathrm{m}}^3$ 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.

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• Density of states
• Electronic structure
• Spin-orbit coupling
• First-principles calculations