Marina A. Zhuravleva

Flux synthesis, structure and physical properties of new pseudo-binary REAl3−xGex compounds

Abstract New compounds in the system RE-Al-Ge (RE=Tb, Gd, Ho) were prepared in molten aluminum. Large, (up to 5 mm) single crystals of new pseudo-binary phases GdAl3−xGex, (x=0.1), TbAl3−xGex, (x=0.3), and HoAl3−xGex, (x=0.2) were recovered in high yield. The crystal structures were refined by single crystal X-ray diffraction techniques, and found to vary as a function of rare-earth element. Thus, GdAl3−xGex crystallizes in the Ni3Sn structure type (P63/mmc) of GdAl3. For the TbAl3−xGex the BaPb3 structure type (R-3m) is adopted, as it is for TbAl3. In the case of HoAl3−xGex, the structure type of HoAl3 is not stabilized, and the compound crystallizes in the BaPb3 structure (R-3m). Crystal data: GdAl3−xGex a=6.3115(4) A, c=4.6052(4) A, V=158.87(2) A3, P63/mmc (No. 194, Z=2); TbAl3−xGex a=6.1956(9) A, c=21.025(4) A, V=698.9(2) A3, R-3m (No. 166, Z=9); HoAl3−xGex a=6.1579(10) A, c=21.062(5) A, V=691.7(2) A3, R-3m (No. 166, Z=9). Charge transport properties indicate that these materials are good metallic conductors. At low temperatures they order antiferromagnetically, whereas above ∼50 K they are Curie–Weiss paramagnets. The temperature of maximum magnetic susceptibility (Tmax) is 5.93 K, 18.8 K, and 24.0 K for HoAl2.8Ge0.2, TbAl2.7Ge0.3, and GdAl2.9Ge0.1 respectively.

Molten gallium as a non-reactive solvent: Synthesis of the silicides RE2Ni3+xSi5-x (RE = Sm, Gd and Tb)

The use of molten Ga as a non-reactive solvent for the synthesis of intermetallic silicides was demonstrated on the family RE2Ni3+xSi5-x (RE = Sm, Gd and Tb). The structure of Sm2Ni3+xSi5-x was solved from single crystal X-ray data in the orthorhombic space group Ibam, Z = 4, cell parameters a = 9.6396(12); b = 11.3219(14); and c = 5.6967(13) Å . The refinement based on the full-matrix least-squares on F2o [I > 2σ(I)] converged to final residuals R1/wR2 = 0.0206/0.0492. The structure of RE2Ni3+xSi5-x is related to the U2Co3Si5 structure type; however, discrepancies exist between the solution obtained for RE2Ni3+xSi5-x and that reported for U2Co3Si5. The magnetic properties studied on Tb2Ni3+xSi5-x indicate an antiferromagnetic ordering of magnetic moments centered at Tb ions at 13 K, and Curie-Weiss behavior at high temperatures with the effective moment close to that of free Tb3+ ion.