MAGNETIC-ANISOTROPY OF DY2FE17-XGAX COMPOUNDS

The single-phase compounds of Dy2Fe17-xGax (x = 0, 1, 2, 3, 4, 5, 6, 7 and 8) were prepared by are melting. The substitution of Ga in the Dy2Fe17 compound is found to have an important effect on their structure and magnetic properties. Dy2Fe17 sample has the hexagonal Th2Ni17-type structure and the Ga-substituted samples crystallize in the rhombohedral Th2Zn17-type structure. The unit cell volumes increase linearly with increasing gallium concentration. The Curie temperature is found first to increase and then to decrease with increasing gallium content x, attaining a maximum value of 557 K at about x = 3, which is 187K higher than that of Dy2Fe17. The saturation magnetization decreases linearly with increasing gallium content from 15.13 mu(B)/f.u. for x = 0 to -4.27 mu(B)/f.u. for x = 8. For x approximate to 6, the Fe sublattice moment is found to be about equal to the Dy sublattice moment. X-ray diffraction measurements on magnetically aligned powder samples reveal a change in easy magnetization direction, and the samples with x less than or equal to 5 exhibit easy plane anisotropy while the samples with x greater than or equal to 6 exhibit easy c-axis anisotropy at room temperature.