Colossal Magnetoresistance in the Transition-Metal Zintl Compound Eu₁₄MnSb₁₁

Magnetoresistance measurements have been carried out on single-crystal sample of the transition-metal Zintl compound Eu₁₄MnSb₁₁. Eu₁₄MnSb₁₁ is the first compound of the Ca₁₄-AlSb₁₁ structure type in which magnetoresistive effects have been measured. Colossal magnetoresistance (CMR) at 92 K and 5 T with Δρ/ρ(0) = -36% and at 5 K and 5 T with Δρ/ρ(0) = -42% were observed. CMR is observed at the ferromagnetic-paramagnetic phase transition (92 K). A large negative magnetoresistance is observed below the second magnetic transition (15 K) and is attributed to a field-induced antiferromagnetic-ferromagnetic ordering of the Eu²⁺ lattice. The MR is highly anisotropic with respect to the crystallographic axes. A sign change in the curvatures of ρ(H) curves below and above 92 K has been observed, indicating that two different mechanisms are responsible for the magnetic scattering of the carriers in two separate temperature regions.