Coercivity enhancement of the Sm/sub 2/(Fe,Nb)/sub 17/N/sub x/-type materials by twice HDDR processing

In an attempt to achieve finer grain which will improve coercivity in Sm/sub 2/Fe/sub 17/N/sub x/-type material, HDDR of Sm/sub 2/Fe/sub 17/-type alloy was done twice before nitrogenation. It has been found that the nitride prepared from this type of HDDR-treated material exhibited a remarkably higher coercivity (around 19 kOe) compared to that from single HDDR-treated material (around 12 kOe). An explanation of the remarkably enhanced coercivity was given with reference to the recombination in more complete form and finer grain size in the material which was processed twice with HDDR.