NEUTRON-DIFFRACTION STRUCTURAL-ANALYSIS OF Y2FE15T2C (T=AL,GA,SI) ALLOYS

Y2Fe15T2C (T=Al,Ga,Si) crystallize in the rhombohedral Th2Zn17-type st ructure. The refined compositions are in excellent agreement with that of the nominal ones. The site occupancies of the substitutional atoms , (Al, Ga and Si) are found to be similar to those of the correspondin g uncarbided compounds and not changed by the C atoms. That is, Al, Ga and Si all prefer the 18h site at the present substituent content, wh ich appears to be determined by the site environments since the 18h si re has the highest number (3) of rare earth neighbors in the structure . C atoms are found to occupy the octahedral interstitial 9e site (1/2 , 0, 0) which has two rare earth neighbors and four Fe/T neighbors, in all three samples. The Curie temperatures have been measured to be 58 8K, 515K, and 535K for the Ga, Al, and Si samples respectively.