Structure and Ferromagnetism of the Rare-Earth Zintl Compounds: Yb₁₄MnSb₁₁ and Yb₁₄MnBi₁₁

Rare-earth transition metal compounds Yb 14 MnSb 11 and Yb 14 MnBi 11 have been prepared by heating stoichiometric amounts of the elements at 1000−1200 °C. These compounds are isostructural with the Zintl compound Ca 14 AlSb 11 and crystallize in the tetragonal space group I 4 1 / acd ( Z = 8). Single-crystal X-ray data (143 K) were refined for Yb 14 MnSb 11 [ a = 16.615(2) Å, c = 21.948(4) Å, V = 6059(2) Å 3, and R 1/ wR 2 (0.0299/0.0479)] and Yb 14 MnBi 11 [ a = 17.000(3) Å, c = 22.259(6) Å, V = 6433(2) Å 3, R 1/ wR 2 (0.0631/0.133)]. Structural analysis is consistent with Yb 2+ . Temperature-dependent magnetic susceptibility data show that Yb 14 MnSb 11 orders ferromagnetically at 56 K and Yb 14 MnBi 11 has a ferromagnetic transition at 58 K and another transition at 28 K. High-temperature magnetic susceptibility data can be fit with a modified Curie−Weiss law and give μ eff = 4.92(2)μ B and μ eff = 4.9(1)μ B for the Sb and Bi compounds, respectively. This result is consistent with the assignment of Mn 3+ ( d 4 ) and Yb 2+ ( f 14 ). Single-crystal magnetic data provide additional evidence for the magnetic transitions and show that the compounds are magnetically anisotropic.