Effect of additives on the structure and magnetic properties of 1:7 type Sm2Fe15Ga2C3 permanent magnets

Abstract

The effect of M(M=Zr, Cu, Nb) additives on the stability and magnetic properties 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 found to improve the thermal stability significantly, but the addition of Cu was found to decrease the thermal stability of the 1:7 metastable phase. After an appropriate heat treatment, M (Zr, Nb, or Cu)-containing samples exhibit better hard magnetic properties than the M-free sample. The intrinsic coercivity and maximum energy product were found to increase from 3.6 kOe and 59 kJ/m3 for the M-free sample to 4.8 kOe and 88 kJ/m3 for the Zr-containing one. The exchange interaction between the grains or the “exchange spring” behavior is studied according the Kneller and Hawig model and Henkel’s plot. The enhancements of magnetic properties originate from the improvement of the intrinsic magnetic properties as well as the refinement of the microstructure.