Tb/sub 2/Mn/sub 17/C/sub 3-x/ with filled Th/sub 2/Ni/sub 17/-type structure and some structural and magnetic properties of related compounds
The new compounds R/sub 2/Mn/sub 17/C/sub 3-x/ (R = Y, Gd, Tb, Dy, Ho, Er, Tm, Lu) were prepared by reacting the elemental components in an arc-melting furnace with subsequent annealing at temperatures between 400 and 900/sup 0/C. Their crystal structures were determined from single-crystal x-ray diffractometer data of Tb/sub 2/Mn/sub 17/C/sub 3-x/ and refined to a residual of R = 0.035 for 27 variable parameters and 588 structure factors. It is hexagonal, space group P6/sub 3//mmc with the lattice constants a = 873.8(1) pm, c = 851.1(1) pm and Z = 2 formula units per cell. The positions of the metal atoms correspond to those of Th/sub 2/Ni/sub 17/. The carbon atoms are situated in approximately octahedral voids formed by two Tb and a rectangle of Mn atoms. Of these carbon positions 81 (4)% are occupied in the crystal investigated; this corresponds to the composition Tb/sub 2/Mn/sub 17/C/sub 2.43/. The new carbides CeMn/sub 11/C/sub 2-x/, NdMn/sub 11/C/sub 2-x/, ThMn/sub 11/C/sub 2-x/ crystallize with LaMn/sub 11/C/sub 2-x/ (filled BaCd/sub 11/) structure; Th/sub 2/Mn/sub 17/C/sub 3-x/ has Pr/sub 2/Mn/sub 17/C/sub 3-x/ (filled Th/sub 2/Zn/sub 17/) structure. The crystal chemistry of these and other interstitial carbides is discussed. The compounds LaMn/sub 11/C/sub 2-x/, CeMn/sub 11/C/sub 2-x/, Pr/sub 2/Mn/sub 17/C/sub 3-x/, and Tb/sub 2/Mn/sub 17/C/sub 3-x/ are paramagnetic with Curie-Weiss behavior at high temperature and no magnetic order at least above about 100 K. The Mn atoms carry magnetic moments in all four compounds. Down to 1.9 K no transition to a superconducting state could be observed for LaMn/sub 11/C/sub 2-x/, La/sub 2/Mn/sub 17/C/sub 3-x/, Y/sub 2/Mn/sub 17/C/sub 3-x/, or Lu/sub 2/Mn/sub 17/C/sub 3-x/.
- Research Organization:
- Universitaet Muenster, West Germany
- OSTI ID:
- 5762173
- Journal Information:
- J. Solid State Chem.; (United States), Vol. 70:2
- Country of Publication:
- United States
- Language:
- English
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