Abstrakt
A series of new ternary arsenides RECo5As3 (RE = Y, Gd, Tb, Dy, Ho, Er) was synthesized from pure constituents. The crystal structure of TbCo5As3 and ErCo5As3 was determined by X-ray single-crystal diffraction, the structure of the other arsenides was refined from X-ray powder diffraction data.
These compounds are isotypic with the YCo5P3 structure (space group Pnma, Pearson code oP36): a = 12.249(8), b = 3.803(5), c = 10.749(5)angstrom for GdCo5As3; a = 12.2350(10), b = 3.7896(2), c = 10.7290(7) angstrom, (R1 = 0.030 (wR2 = 0.038) for 828 reflections with I-o > 2 sigma(I-o)) for TbCo5As3; a = 12.225(2), b = 3.781(7), c = 10.715(5) angstrom for DyCo5As3; a = 12.214(4), b = 3.775(4), c = 10.709(1) angstrom for HoCo5As3; a = 12.2033(7), b = 3.7685(2), c = 10.7009(4) angstrom, (R1 = 0.039 (wR2 = 0.062) for 921 reflections with I-o > 2 sigma(I-o)) for ErCo5As3. The structure contains distorted trigonal prisms [AsRE2Co4] condensed together by edges from RE atoms to infinite zig-zag chains.
TbCo5As3 was identified as having an antiferromagnetic ground state with the Neel temperature T-N = 55-60 K, which is obscured by spurious metallic Co.