Magnetoresistance effect of La-Ca-Sr-Mn-O perovskites under a very low magnetic field

Abstract

The bulk polycrystalline samples of La0.7Ca0.1Sr0.2MnO3, La0.7Ca0.15Sr0.15MnO3 and La0.7Ca0.25Sr0.05MnO3 have been synthesized by doping La0.7Ca0.3MnO3 with La0.7Sr0.3MnO3 (second doping method). The MR effect for three samples has been investigated under low magnetic field. A quite large (-19.5%) negative magnetoresistance ratio has been obtained in La0.7Ca0.25Sr0.05MnO3 under only 0.1 T magnetic field. The MR peaks relative to the preparation method are observed in all three samples around temperature 100 K, well below the insulator-metal transition temperature Tt(260-270 K), and it is not affected very much by Sr2+ density. MR exists in a wide temperature range. The MR effect can be explained as a result of the presence of grain boundaries.