Magnetic Properties of R2T17-Type Compounds Dy2Fe17-x-yAlx with Iron Deficiency

The ternary R
₂
T
₁₇
-type alloys Dy
₂
Fe
_17-x-y
Al
_x
with an Fe deficiency have been studied by means of X-ray diffraction and magnetization measurements. The single phase boundary of the R
₂
T
₁₇
-type structure was determined to be near the composition Dy
₂
Fe
₉
Al
_x
for x≥4 and near Dy
₂
Fe
_13-x
Al
_x
for x≤4. The crystal structure is of the Th
₂
Ni
₁₇
type for alloys with x≤5, and of the Th
₂
Zn
₁₇
type for 6≤×≤8. Thermomagnetic curves show that the magnetism changes from P-type to N-type ferrimagnetism with increasing Al content x. Three types of spin arrangements, in which x≤2, 2≪×≤5 and 6≤×≤8, were proposed on the basis of the magnetic studies. It was concluded that the substitution of Al for Fe causes a decrease in the Fe magnetic moment, but that an Fe deficiency causes an increase in the Fe magnetic moment.