Vmt. Thiede et al., EUTA2AL20, CA6W4AL43 AND OTHER COMPOUNDS WITH CECR2AL20 AND HO6MO4AL43 TYPE STRUCTURES AND SOME MAGNETIC-PROPERTIES OF THESE COMPOUNDS, Journal of alloys and compounds, 267(1-2), 1998, pp. 23-31
The 25 new compounds CaT2Al20 (T=Ti, Nb, Ta, Mo), LnT(2)Al(20) (Ln=La,
Ce, Pr, Nd, Sm, Eu; T=Nb, Ta), SmCr2Al20, TbCr2Al20, Ca6W4Al43, Y6Nb4
Al43, Y6Ta4Al43, and Ln(6)Mn(4)Al(43) (Ln=Ho-Yb) have been prepared by
reaction of the elemental components in alumina crucibles under argon
. They crystallize with CeCr2Al20 and Ho6Mo4Al43 type structures, resp
ectively, which were refined from single-crystal X-ray data of EuTa2Al
20 (Fd (3) over bar m, a=1478.3(1) pm, R=0.025 for 312 structure facto
rs and 15 variable parameters) and Ca6W4Al43 (P6(3)/mcm, a=1108.4(4) p
m, c=1778.8(6) pm, R=0.010 for 849 F values and 53 variables). All ato
mic positions are fully occupied, with the exception of one aluminium
site of EuTa2Al20, which has an occupancy of only 81(2)%. The compound
s LnCr(2)Al(20) (Ln=La-Nd, Eu) and LnV(2)Al(20) (Ln=La-Pr, Eu-Tb) are
confirmed. The cell volumes of the cerium, europium and ytterbium comp
ounds LnT(2)Al(20) (Ln=Ce, Eu; T=Ti, V, Nb, Ta, Cr, Mo, W), YbTi2Al20
and Yb6Mn4Al43 deviate from the smooth functions observed for the cell
volumes of the compounds with the typically trivalent rare earth elem
ents. Magnetic susceptibility data, measured with a SQUID magnetometer
, show Pauli paramagnetism for LaTi2Al20, LaMo2Al20, CeTi2Al20, CeV2Al
20, and CeMo2Al20, thus indicating cerium to be tetravalent in agreeme
nt with the cell volumes of these compounds. The magnetic susceptibili
ties of EuTi(2)Al(20)and EuMo2Al20 follow the Curie-Weiss law; their m
agnetic moments correspond to divalent europium. (C) 1998 Elsevier Sci
ence S.A.