Ternary Antimonides RE₄T₇Sb₆ (RE=Gd–Lu; T =Ru, Rh) with Cubic U₄Re₇Si₆-type Structure

Abstract

The ternary antimonides RE 4 T 7 Sb 6 (RE=Gd-Lu; T =Ru, Rh) have been synthesized from the elements by arc-melting and subsequent annealing in an induction furnace. The samples have been characterized by powder X-ray diffraction. Four structures were refined on the basis of single-crystal X-ray diffractometer data: U 4 Re 7 Si 6 type, space group Im3m with a=862.9(2) pm, wR2=0.0296, 163 F 2 values for Er 4 Ru 7 Sb 6 ; a=864.1(1) pm, wR2=0.1423, 153 F 2 values for Yb 4 Ru 7 Sb 6 ; a=872.0(2) pm, wR2=0.0427, 172 F 2 values for Tb 4 Rh 7 Sb 6 ; and a=868.0(2) pm, wR2=0.0529, 154 F 2 values for Er 4 Rh 7 Sb 6 , with 10 variables per refinement. The structures have T1@Sb 6 octahedra and slightly distorted RE@T2 6 Sb 6 cuboctahedra as building units. The distorted cuboctahedra are condensed via all trapezoidal faces, and this network leaves octahedral voids for the T1 atoms. The ruthenium-based series of compounds was studied by temperature-dependent magnetic susceptibility measurements. Lu 4 Ru 7 Sb 6 is Pauli-paramagnetic. The antimonides RE 4 Ru 7 Sb 6 with RE=Dy, Ho, Er, and Tm show Curie-Weiss paramagnetism. Antiferromagnetic ordering occurs at 10.0(5), 5.1(5) and 4.0(5) K for Dy 4 Ru 7 Sb 6 , Ho 4 Ru 7 Sb 6 and Er 4 Ru 7 Sb 6 , respectively, while Tm 4 Ru 7 Sb 6 remains paramagnetic. Yb 4 Ru 7 Sb 6 is an intermediate-valent compound with a reduced magnetic moment of 3.71(1) μ B per Yb as compared to 4.54 μ B for a free Yb 3+ ion