Structural and magnetic properties of Sm2Fe16MAl2 (M = Mn, Mo, Ni) and their carbides

Structural and magnetic properties of off-stoichiometric 2:17-type compound s Sm2Fe16MAl2 (M = Mn, Mo, Ni) and their carbides were studied using X-ray powder diffractometry, magnetization measurement, thermomagnetic analysis, and differential thermal analysis, All these compounds had the Th2Zn17-type structure. When Mo was added into the parent compound Sm2Fe17Al2, the unit cell was enlarged by 0.4%, larger than those of M = Ni, Mn, However, the C urie temperature T-c and saturation magnetization M-s of Sm2Fe16MoAl2 were lower than the parent because Mo atom had not effectively increased the sep aration of Fe-Ire pairs. When C was added to the parent and the Sm2Fe16MAl2 , an increase in the volume of the unit cell and T-c, and a decrease of M-s were observed, The carbide of the parent had the largest cell dilation of 2.11%, which also exhibited relatively high T-c and M-s, When M = Ni, its c arbide had the largest M,, indicating that the addition of Ni had enhanced the ferromagnetic coupling, It was also found that Sm2Fe16MnAl2C1.5 was mor e stable than the other compounds, and that it decomposed at about 950 degr eesC.