Large magnetoresistance in three dimensionally ordered macroporous perovskite manganites prepared by a colloidal templating method

Abstract

Macroporous perovskite manganites La_0.7Ca_0.3−xSr_xMnO₃, whose pores are highly ordered, have been prepared by a colloidal templating technique. The pore size was found to be about 400 nm and the wall thickness was in the range of 40–60 nm. As the Sr content increased, the ferromagnetic transition temperature (T_C) gradually rose to 350 K. The x = 0.1 sample exhibited a metal–insulator transition near T_C. A large negative magnetoresistance (MR), which was independent of temperature, was also observed below T_C. The large MR might be ascribed to spin polarized tunneling at the nano-sized grain boundaries.