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 Ca14AlSb11 structure type in which magnetoresistive effects have been measured. Colossal magnetoresistance (CMR) at 92 K and 5 T with Delta rho/rho(0) = -36% and at 5 K and 5 T with Delta rho/rho(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 rho(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.