Synthesis, magnetic properties, and colossal magnetoresistance ofEu13.97Gd0.03MnSb11

The synthesis, crystal structure, magnetization, and resistivity of Gd-doped ${\mathrm{Eu}}_{14}{\mathrm{MnSb}}_{11}{,\mathrm{}\mathrm{Eu}}_{13.97}{\mathrm{Gd}}_{0.03}{\mathrm{MnSb}}_{11},$ are reported and compared to ${\mathrm{Eu}}_{14}{\mathrm{MnSb}}_{11}$ and ${\mathrm{Eu}}_{14}{\mathrm{MnBi}}_{11}.$ All three compounds are isostructural with the Zintl compound ${\mathrm{Ca}}_{14}{\mathrm{AlSb}}_{11}.$ The Gd-doped Eu transition metal Zintl compound crystallizes in the tetragonal space group ${I4}_{1}/\mathit{acd}$ with $a=17.338(3)\AA{}$ and $c=22.691(5)\AA{},$ where Gd partially replaces Eu in the structure. The compound displays three magnetic phase transitions: a ferromagnetic transition near 80 K, an apparent antiferromagnetic transition at a field-dependent ${T}_{N}$ ${(T}_{N}=30\mathrm{K}$ in zero field), and a spin-reorientation transition with a transition temperature that is near 15 K in zero field but is also field dependent. Measurements of both zero-field resistivity for $5l~Tl~300\mathrm{K}$ and the magnetoresistance in fields up to 5 T for the same temperatures are presented. Negative magnetoresistance is observed over a wide range of temperatures below 200 K.