Ternary rare-earth selenides with the U3ScS6 structure type: synthesis, characterization, and some magnetic properties of Ln3TSe6 (Ln = Sm, Gd; T = In, Cr) and Tb3CrSe6.
The new compounds Ln3TSe6 (Ln = Sm, Gd; T = In, Cr) and Tb3CrSe6 have been synthesized by the solid-state reactions of the elements at 850 degrees C. A KBr flux was used to promote crystal growth. These isostructural compounds crystallize with the U3ScS6 structure type. The crystal structure is built from LnSe7 pseudo-octahedra or LnSe8 bicapped trigonal prisms and TSe6 octahedra. Magnetic measurements show that Sm3TSe6 (T = In, Cr) and Tb3CrSe6 are paramagnetic down to 5 K whereas Gd3CrSe6 undergoes an antiferromagnetic transition at 10 K. Crystal data: orthorhombic, Pnnm, Z = 4, T = -120 degrees C, (compound, a (A), b (A), c (A))-Sm3InSe6, 14.177(3), 17.352(4), 4.0625(8); Gd3InSe6, 14.071(3), 17.286(4), 4.0202(8); Sm3CrSe6, 14.032(3), 16.782(3), 3.9841(8); Gd3CrSe6, 13.938(3), 16.780(3), 3.9559(8); Tb3CrSe6, 13.885(3), 16.672(3), 3.9215(8).
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Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, USA.
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