Electronic transport on doped La0,6D0,4MnO3 ceramic manganites

We have studied magnetotransport in a set of nanocrystalline samples of composition La0,6D0,4MnO3, where the divalent ion is changed. Magnetization results show a paramagnetic transition near room temperature and large differences for ZFC and FC routes. The resistivity shows a broad peak at temperatures between 178 and 267 K, and a minimum near 30 K. Under a magnetic field we see a significant drop in the resistivity with a larger metallic region. The data show that at low temperatures inter-grain tunneling model applies, providing good crossover to the metallic range where scattering in the presence of disorder takes place.