Room temperature magneto-resistance and temperature coefficient of resistance in La0.7Ca0.3−xAgxMnO3 thin films

Abstract

We investigate the magnetotransport properties of La0.7Ca0.3−xAgxMnO3 (0⩽x⩽0.3) polycrystalline films prepared by spray pyrolysis. The virgin La0.7Ca0.3MnO3 (LCMO) (x=0.0) film shows paramagnetic-ferromagnetic [insulator-metal (IM)] transition at TC∼260K (TIM∼245K). Ag doping induces appreciable enhancement in TC∕TIM and interestingly TIM of Ag doped films is higher than the corresponding TC value. In the 30% Ag doped film IM transition occurs at ∼325K which is ∼10K higher than its TC∼315K. Strong irreversibility is observed in zero field cooled–field cooled magnetization of all the films and the irreversibility temperature Tirr>TC increases with Ag doping. This suggests the formation of magnetic clusters above TC. The pure LCMO film exhibits small magnetoresistance (MR) ∼20% and rather poor temperature coefficient of resistance (TCR) in the vicinity of the room temperature. In contrast, around room temperature the Ag doped films show large MR which is ∼60% for x=0.15 and decreases to ∼30% for the pure Ag doped film. Ag doped films also have good TCR ∼4%∕K in the vicinity of room temperature.