R₂Fe₁₇ Intermetallics: A Review

R₂Fe₁₇ (where R stands for rare earth or Y) intermetallics are fascinating iron-rich compounds knownfor their high saturation magnetization and intriguing physics that stem from competing exchange interactions,various Fe crystallographic sites, and structural polymorphism (think rhombohedral Th₂Zn₁₇ versus hexagonalTh₂Ni₁₇). This review dives into the structural chemistry, magnetic behavior, and the different methods used totweak these properties, including substitution (with elements like Co, Al, Ga, Si), off-stoichiometry,nitriding/hydrogenation, nanostructuring, and processing techniques. We particularly highlight how substitutionimpacts the Curie temperature, magnetocrystalline anisotropy, magnetization, and magnetovolume effects, witha keen focus on the effects of Co/Ga/Si/Al substitution and the latest off-stoichiometric studies. The review alsodiscusses representative experimental, neutron, and theoretical works, and includes a carefully curatedbibliography of over 50 papers for researchers who are stepping into this exciting field