Effect of additives on the structure and magnetic properties of 1 : 7 typeSm2Fe15Ga2C3 permanent magnets

The effect of M(M=Zr, Cu, Nb) additives on the stability and magnetic prope rties of melt-spun nanocrystalline Sm2Fe15Ga2C3 ribbons with the 1:7-.type structure has been investigated. The addition of 1 at. % of Zr or Nb was fo und to improve the thermal stability significantly, but the addition of Cu was found to decrease the thermal stability of the 1:7 metastable phase. Af ter an appropriate heat treatment, M (Zr, Nb, or Cu)-containing samples exh ibit better hard magnetic properties than the M-free sample. The intrinsic coercivity and maximum energy product were found to increase from 3.6 kOe a nd 59 kJ/m(3) for the M-free sample to 4.8 kOe and 88 kJm(3) for the Zr-con taining one. The exchange interaction between the grains or the "exchange s pring" behavior is studied according the Kneller and Hawig model and Henkel 's plot. The enhancements of magnetic properties originate from the improve ment of the intrinsic magnetic properties as well as the refinement of the microstructure. (C) 2000 American Institute of Physics. [S0021-8979(00)0791 9-6].