Room temperature magneto-resistance and temperature coefficient of resistance in la0.7Ca0.3-xAgxMnO3 thin films

Abstract

We investigate the magnetotransport properties of La0.7Ca 0.3-xAgxMnO3 (0 ≤ x ≤ 0.3) polycrystalline films prepared by spray pyrolysis. The virgin La 0.7Ca0.3MnO3 (LCMO) (x=0.0) film shows paramagnetic-ferromagnetic [insulator-metal (IM)] transition at TC ∼ 260 K (TIM ∼245 K). 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 ∼325 K which is ∼ 10 K higher than its TC ∼315 K. 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. © 2007 American Institute of Physics.