Neutron diffraction structural analysis of Y/sub 2/Fe/sub 15/T/sub 2/C (T=Al,Ga,Si) alloys

Y/sub 2/Fe/sub 15/T/sub 2/C (T=Al,Ga,Si) crystallize in the rhombohedral Th/sub 2/Zn/sub 17/-type structure. 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 corresponding 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, which appears to be determined by the site environments since the 18h site 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 588 K, 515 K, and 535 K for the Ga, Al, and Si samples respectively.