EFFECT OF THE SUBSTITUTION OF GA ON THE STRUCTURE AND MAGNETIC-PROPERTIES OF DY2FE17 COMPOUND

Dy2Fe17-xGax (x = 0, 1, 2, 3, 4, 5 and 6) compounds were prepared by a re melting. These compounds are of single phase, having a hexagonal Th -2 Ni-17-type structure fox x = 0 and rhombohedral Th2Zn17-type struct ure for x greater than or equal to 1. The substitution of Ga for Fe in the Dy2Fe17 leads to a linear increase of unit-cell volumes. The satu ration magnetization M(s) at 1.5 K is found to decrease linearly with increasing Ga concentration, from 65 emu/g for x = 0 to 5 emu/g for x = 6; and the Fe magnetic moment mu(Fe), is almost independent of Ga co ncentration. The Curie temperature T-c is found first to increase with increasing Ga content x, and goes through a maximum value of 559 K at about x = 3, then decreases. The sharp increase of T-c at lower Ga co ntent may result from the increase of unit cell volumes. Dy2Fe17-xGax compounds with x less than or equal to 5 exhibit easy plane anisotropy at room temperature, and those with x = 6 possess easy-axis.