Figure 4.

(Left) Curie temperatures for different rare-earth atoms, for $R_2$Fe${}_{17}$ and RFe${}_{10.5}$Mo${}_{1.5}$[28,30,75,96,97,98]. (Right) Exchange interaction $J_{\mathrm{T}\text{-}\mathrm{T}}$ vs. distances between transition metal atoms (T–T) for Sm${}_2{T}_{17}$. For interatomic T–T distances less than 2.45 Å the exchange interaction ($J_{\mathrm{T}\text{-}\mathrm{T}}$) is negative, while $J_{\mathrm{T}\text{-}\mathrm{T}}$ is positive in the opposite case [94].