EFFECTS OF GA SUBSTITUTION IN ER2FE17C2 COMPOUNDS ON THE STRUCTURE AND MAGNETIC-PROPERTIES

We have studied the structure and magnetic properties of Er2Fe17-xGaxC 2 (x = 0, 1, 2, 3, 4, 5 and 6) compounds by means of X-ray diffraction and magnetic measurements. Crystal structure studies have shown that these carbides have a rhombohedral Th2Zn17-type structure. The lattice constants and the unit cell volumes increase linearly with increasing Ga concentration x. The Curie temperature of Er2Fe17-xGaxC2 with x le ss than or equal to 2 is almost independent of Ga concentration, havin g a T-C higher than 600 K, and then decreases rapidly with increasing Ga concentration. An monotonic decrease of the saturation magnetizatio n with x is observed when non-magnetic Ga atom is substituted for Fe. Er2Fe17-xGaxC2 samples with x less than or equal to 5 exhibit a spin r eorientation transition. The spin reorientation temperature T-sr is fo und first to increase, goes through a maximum value of 227 K at about x = 2, and then decreases monotonically with increasing Ga concentrati on.