Abstract The physical properties of the La 0.6 Y 0.1 Ca 0.3 MnO 3 compound have been investigated, focusing on the magnetoresistance phenomenon studied by both dc and ac electrical transport measurements. X-ray diffraction and scanning electron microscopy analysis of ceramic samples prepared by the sol-gel method revealed that specimens are single phase and have average grain size of~0.5 lm. Magnetization and 4-probe dc electrical resistivity q(T,H) experiments showed that a ferromagnetic transition at T C~1 70 K is closely related to a metal-insulator (MI) transition occurring at essentially the same temperature T MI . The magnetoresistance effect was found to be more pronounced at low applied fields (H £ 2.5 T) and temperatures close to the MI transition. The ac electrical transport was investigated by impedance spectroscopy Z(f,T,H) under applied magnetic field H up to 1 T. The Z(f,T,H) data exhibited two well-defined relaxation processes that exhibit different behaviors depending on the temperature and applied magnetic field. Pronounced effects were observed close to T C and were associated with the coexistence of clusters with different electronic and magnetic properties. In addition, the appreciable decrease of the electrical permittivity e¢(T,H) is consistent with changes in the concentration of e g mobile holes, a feature much more pronounced close to T C
