Structural and low-temperature magnetic studies on compounds Sm2Fe17 with aluminium substitution for iron

Aluminium substitution for iron in Sm2Fe17results in stabilization of the Th2Zn17structure. Compounds are homogeneous from x=0.20 to x=0.50 in Smsub(0.105)Fesub(0.895-x)Alsub(x) when annealed at 8000C. In this structure, Fe and Al are statistically distributed on 6(c), 9(d), 18(f) and 18(h) sites. Materials with x=0-0.15 are composed of the Th2Zn17type and Fe. The magnetic hardness at cryogenic temperatures increases rapidly around a composition with x=0.30. A value of coercive force, Hsub(c)=15kOe, is obtained both on bulk and powder material with x=0.50 at 4.2K. This low-temperature magnetic hardness appears to be connected with the presence of highly energetic domain walls. The mechanism of demagnetization involves domain nucleation, in contrast with Smsub(0.167)Cosub(0.833-x)Alsub(x) where demagnetization is predominantly governed by domain wall pinning. (Auth.)