Effect of sintering temperature on electrical transport of La0.67Ca0.33MnO3 granular system with 4% CuO addition

The granular systems of La0.67Ca0.33MnO3 (LCMO) with 4% CuO addition were fabricated by three steps. Firstly, the LCMO particles were prepared and sintered at temperatures of 600 °C (Ts6), 1000 °C (Ts10), 1200 °C (Ts12) and 1400 °C (Ts14). Experimental results show that with the increment of sintering temperature, the particle size of the pre-prepared LCMO also increases, which plays a key role on electrical transport of the final composites. It is found that sample Ts14 exhibits two transition peaks both in ρ–T and MR0–T curves, while sample Ts12 only shows two transition peaks in MR0–T curve. Here MR0 is the abbreviation of magnetoresistance. These two transition peaks are ascribed to the intrinsic and extrinsic effects, respectively. For sample Ts6, Cu2+ ions mainly enter into the lattice of LCMO to form with La0.67Ca0.33Mn1−xCuxO3. Specially, it is interesting to observe the MR0 effect of ∼90% at 0.3 T for sample Ts10 at the vicinity of insulator-metal transition temperature TIM, where considerable thermal hysteresis also appears. Such enhancement of MR effect is attributed to the field suppression of spin disordering especially at grain boundaries caused by CuO addition.