Substitutional and interstitial modification of Nd5Fe17

The intermetallic compound Nd5Fe17 has potentially important magnetic properties and is being investigated as a possible permanent magnet material, since the partial replacement of Nd by Sm leads to uniaxial anisotropy. We have produced and studied materials with compositions Nd5(Fe,X)17 (X = Co, Mn, Ti, Cr, Al), (Nd,Sm)5Fe17, and (Nd,Sm)5(Fe,X)17 (X = Co, Ti). Only (Nd,Sm)5(Fe,Ti)17 has substantially improved magnetic properties in comparison with binary Nd5Fe17. Ti substitution, however, leads to a more rapid formation of the 5:17 phase than in the binary compound. This paper also reports structural and magnetic measurements on deuterided Nd5Fe17 and (Nd,Sm)5(Fe,Ti)17. The deuterides are similar to the hydrides in that 14–16 atoms are absorbed per formula unit. The increases in the lattice parameters were larger than in the binary compound: Δa/a = 4.3% and Δc/c = 4.6% for Nd5Fe17D15.5 and Δa/a = 5.3% and Δc/c = 5.2% for (Nd,Sm)5(Fe,Ti)17D14. For Nd5Fe17, deuterium absorption results in a ∼6% increase in Ms, while, for (Nd,Sm)5(Fe,Ti)17, Ms increases by less than 1%. These measurements are consistent with Mössbauer spectroscopy results presented here. These results are discussed in light of recent band structure calculations. (Nd,Sm)5(Fe,Ti)17 was reacted with NaN3 in an attempt to produce a stable 5:17 nitride. Materials reacted at temperatures 523–623 K for 3–20 h showed multiple phases. One of the phases had Tc ∼ 571 K.