Magnetic properties of Sm<inf>2+α</inf>Fe<inf>17</inf>N<inf>x</inf> powders prepared from bulk and strip-cast alloys

The current research paper analyzed the structure and magnetic properties of bulk Sm2.40Fe17 and Strip-Cast (SC) Sm2.08Fe17 alloys. Strip Cast alloy was found to have low volume fraction of the secondary phases (SmFe3 and α-Fe phase) with finer grain size (2–3 times lower) in comparison with bulk alloy. Owing to such microstructural features, the Strip Cast alloy has the advantages of low nitrogenation temperature, reduced time duration for nitrogenation and effective nitrogenation of even coarser particles which tend to result in better magnetic properties compared to bulk alloy. The additional ball milling of the SC Sm2.08Fe17N3 powder in toluene, after adding 0.5% Zn stearate, resulted in achieving a coercivity of 9.3 kOe. The angular dependence of coercivity measurements indicates that the dominant coercivity mechanism is the nucleation of reverse domains at defects for coarser particles and non-uniform rotation of magnetic moments for the sub-micron level single-domain particles.