Review of Research and Development of Sm2Fe17Nx Hard Magnetic Material

Research and development of Sm
2
Fe
17
N
x
hard magnetic materials is reviewed. In order to investigate the effects of different interstitial elements on the Th
2
Zn
17
parent crystal structure and on the magnetic properties of the material, research on Sm
2
Fe
17
C
y
compounds is also reviewed. The lattice constants a and c of Sm
2
Fe
17
C
y
compounds (y≪1.5) gradually increase with increasing carbon content. Both Sm
2
Fe
17
N
x
and Sm
2
Fe
17
C
y
(x,y≫2.0) compounds exhibited nearly constant lattice expansion rates of 2.3% along the a-axis and 1.7% along the c-axis. No report has appeared on compounds for which 1.5≪(x or y)≪2. In Sm
2
Fe
17
C
y
(y≪1.5) compounds, the unit cell volume and Curie temperature (T
c
) increase with increasing carbon content. In Sm
2
Fe
17
N
x
(2.1≪x≪3) compounds, however, a nearly constant unit cell volume and T
c
are reported. The differences in the magnetic properties of Sm
2
Fe
17
N
x
specimens prepared from the different starting alloys produced in various processes are reviewed. The mechanism of nitrogenation under various gas atmospheric conditions is also discussed and reviewed.