Ternary rare-earth selenides with the U3ScS6 structure type: Synthesis, characterization, and some magnetic properties of Ln(3)TSe(6) (Ln = Sm, Gd; T= In, Cr) and Tb3CrSe6

The new compounds Ln(3)TSe(6) (Ln = Sm, Gd; T = In, Cr) and Tb3CrSe6 have b een synthesized by the solid-state reactions of the elements at 850 degrees C. A KBr flux was used to promote crystal growth. These isostructural comp ounds crystallize with the U3SCS6 structure type. The crystal structure is built from LnSe(7) pseudo-octahedra or LnSe(8) bicapped trigonal prisms and TSe6 octahedra. Magnetic measurements show that Sm3TSe6 (T = In, Cr) and T b3CrSe6 are paramagnetic down to 5 K whereas Gd3CrSe6 undergoes an antiferr omagnetic transition at 10 K. Crystal data: orthorhombic, Pnnm, Z = 4, T = -120 degrees C, (compound, a (Angstrom), b (Angstrom), c (Angstrom))-Sm3InS e6, 14.177(3), 17.352(4), 4.0625(8): Gd3InSe6, 14.071(3), 17.286(4), 9.0202 (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).