The microstructure and electronic transport properties of mechanical milled La2/3Ca1/3MnO3 perovskites

Polycrystalline perovskite La2/3Ca1/3MnO3 samples were synthesized by mechanical ball milling for 10 h and subsequent sintering at the temperatures from 850 to 1400 °C. The microstructure and electronic transport properties were studied. All samples exhibited the metal-to-insulator transition at the temperature, which is nearly the same as that of La2/3Ca1/3MnO3 single crystal. The samples with grain size of 170-2500 nm showed the extrinsic magnetoresistance (MR) over a wide temperature range from the metal-to-insulator temperature (TMI) to 100 K in an applied field of 3 kOe. The samples with the grain size above 4500 nm showed the intrinsic MR near TMI. A clear image of the coexistence of intrinsic MR and extrinsic MR were observed.