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

The ternary R2T17-type alloys Dy2Fe17-x-yAlx with an Fe deficiency have been studied by means of X-ray diffraction and magnetization measurements. The single phase boundary of the R2T17-type structure was determined to be near the composition Dy2Fe9Alx for x¿4 and near Dy2Fe13-xAlx for x¿4. The crystal structure is of the Th2Ni17 type for alloys with x¿5, and of the Th2Zn17 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.