Neutron Diffraction Study of the Ternary Transition Metal Zintl Compound Ca14MnSb11

The magnetic ordering of the tetragonal Ca14MnSb11 compound (space group I41/acd) has been determined by high-resolution neutron diffraction on powder samples. Neutron data were obtained at temperatures of 1.4, 10, 95 K, and room temperature. Refinement of the magnetic structure reveals a ferromagnetic ordering of Mn magnetic moments lying in the a-b plane below the TC of 63 K. The low-temperature-ordered magnetic moment on the Mn ion is 3.4(2) ~B at 1.4 K. The results are confirmed by magnetic susceptibility measurements, which show that the easy magnetization direction of the compound is perpendicular to the c-axis and the system orders ferromagnetically at 63 K, in good agreement with neutron diffraction results. A large negative magnetoresistance effect (deltarho/rho(H)=-34.4%) at the magnetic transition temperature is observed in applied magnetic fields up to 6 T.