Structure and ferromagnetism of the rare-earth Zintl compounds: Yb14MnSb11 and Yb14MnBi11

Rare-earth transition metal compounds Yb14MnSb11 and Yb14MnBi11 have been prepared by heating stoichiometric amounts of the elements at 1000--1200 C. These compounds are isostructural with the Zintl compound Ca14AlSb11 and crystallize in the tetragonal space group I41/acd (Z = 8). Single-crystal X-ray data (143 K) were refined for Yb14MnSb11. Structural analysis is consistent with Yb2+. Temperature-dependent magnetic susceptibility data show that Yb14MnSb11 orders ferromagnetically at 56 K and Yb14MnBi11 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 μeff = 4.92(2)μB and μeff = 4.9(1)μB for the Sb and Bi compounds, respectively. This result is consistent with the assignment of Mn3+ (d4) and Yb2+ (f14). Single-crystal magnetic data provide additional evidence for the magnetic transitions and show that the compounds are magnetically anisotropic