Magnetostrictions of Sm2Fe17 and Sm2Fe17N3.

The magnetostrictions of Sm2Fe17N3 and Sm2Fe17 were investigated using strain gauge rotating-sample methods. In a magnetic field of 8 T, the magnetostriction \lambda t\ (\lambda {\rm t} = \lambda // - \lambda \bot) of Sm2Fe17 is about -155 \times 10 ^-6 at 300 K. It becomes positive after nitrogenation [Sm2Fe17N3, \lambda t is about + 44 \times 10 ^-6 at 300 K (H = 8 T)] 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 \bot 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%. [ABSTRACT FROM AUTHOR]