STUDIES OF V, NB, CR, AND ZR SUBSTITUTED 2 17 COMPOUNDS AND THEIR CARBIDES USING NEUTRON-DIFFRACTION/

Samples of Nd2Fe17-xTxCy with T=V, Nb, Cr, and Zr were prepared by mel ting of the constituent elements including C and studied by neutron di ffraction. Comparing with their uncarbided counterparts, we found that the substituents transfer, more or less, from the 6c site to the 18f and 18h sites with the introduction of C atoms. This behavior appears to relate to the electronegativities between the C atoms and the early transition series elements because the 18f and 18h sites are near nei ghbors of the interstitial C site. However, the C effects in the V, Nb , Cr, and Zr samples are not as strong as those in Ti samples. SQUID m easurements show that the Curie temperatures of these samples depend o n both the interstitial C atoms and the substituents. (C) 1997 America n Institute of Physics.