Electrical transport properties of Sm-doped La0.7Ca0.3MnO3 polycrystalline ceramics

Improving the magnetoresistance effect of perovskite ceramic materials under a low applied magnetic field to expand its application range is one of the main research directions of this type of material. In this study, La0.7Ca0.3MnO3 was doped with different levels of Sm by the sol-gel method to yield a series of La0.7-xSmxCa0.3MnO3 (LSCMO) polycrystalline ceramics. X-ray diffraction (XRD) results revealed that LSCMO ceramics possessed standard perovskite structures. Scanning electron microscopy (SEM) showed grains closely connected without obvious holes. In addition, the grain size gradually decreased with the increase in Sm doping content. The resistivity temperature curves displayed a clear metal-insulator transition behavior of LSCMO accompanied by a steep change from ferromagnetic to paramagnetic behavior (FM-PM). The metal-insulator transition temperature (Tp) values of the as-obtained LSCMO gradually shifted toward lower temperatures with increase in Sm content. Moreover, resistivity temperature coefficient (TCR) and magnetoresistance (MR) values also gradually increased with Sm doping content. The transport properties in polycrystalline ceramics could be adequately explained by the double exchange model, which would be useful for interpreting the CMR effects when used in magnetic devices.