Structure and properties of the transition-metal zintl compounds: A₁₄MnBi₁₁ (A = Ca, Sr, Ba)

A₁₄MnBi₁₁ (A = Ca, Sr, Ba) is synthesized by reacting the elements in stoichiometric amounts at high temperatures (950-1350°C). Single-crystal X-ray diffraction data (130 K, a = 17.002 (6) Å, c = 22.422 (7) Å (Ca); a = 17.820 (6) Å, c = 23.394 (6) Å (Sr); a = 18.633 (8) Å, c = 24.340 (10) Å (Ba)) were refined (tetragonal, I4₁/acd(142), Z = 8, R = 5.4%, R_w = 5.9% (Ca), R = 4.1%, R_w = 4.7% (Sr), R = 5.1%, R_w = 4.9% (Ba)) and showed these compounds to be isostructural to the main-group analogues, Ca₁₄AlSb₁₁ and A₁₄GaAs₁₁ (A = Ca, Sr). Magnetization measurements performed on powder samples have shown that Ca₁₄MnBi₁₁ and Sr₁₄MnBi₁₁ are ferromagnets and that Ba₁₄MnBi₁₁ is an antiferromagnet. The magnetic coupling between Mn ions is attributed to an RKKY interaction, and thus metallic behavior is expected. The temperature dependence of the resistivity of pressed pellets is presented and suggests that all three compounds are metals.