Magnetostrictions of Sm2Fe17 and Sm2Fe17N3

The magnetostrictions of Sm2Fe17N3 and Sm2Fe17 were investigated using strain gauge rotating-sample methods. In a magnetic field of 8T, the magnetostriction lambda(t) (lambda(t) = lambda(//) - lambda(perpendicular to) of Sm2Fe17 is about -155 x 10(-6) at 300 K. It becomes positive after nitrogenation [Sm2Fe17N3, lambda(t) is about +44 x 10(-6) at 300 K (H = 8T)] due to the crystal field effect and the exchange striction. It was noticed that inverse magnetostriction effect can be used to increase the magnetic alignment and remanence of the bonded magnets. As a result, transverse die-pressing (H perpendicular to P) was very effective in increasing the degree of magnetic alignment of Sm2Fe17N3 powders, yielding remanence higher than that obtained by axial die-pressing (H//P). By increasing the degree of magnetic alignment of powders, the maximum energy product (BH)(max) of Sm2Fe17N3 bonded magnet was improved by 15%.