Electrical Properties of La_(0.7)Ba_(0.297)Ca_(0.003)Mn03 Obtained by Low Temperature Sol-Gel Synthesis

摘要

A compound of La_(0.7)Ba_(0.297)Ca_(0.003)MnO_3 was obtained by low temperature sol-gel synthesis. The structural and electrical properties of the material were systematically studied. La_(0.7)B_(a0.297)Ca_(0.003)MnO_3 material is a member of mixed valence manganites which has a perovskite structure. The general structure isAMnO3 (A=trivalent rare earth with divalent ion-doped such as Sr~(2+), Ca~(2+), Ba~(2+), etc). The previous study proved that doped Ca~(2+) ion to the La_(0.7)Ba_(0.3)MnO_3 material increased its CMR effect and MCE effect and decreased its T_c become near room temperature. CMR effect is change of resistivity due to external magnetic field in the perovskite-based material. Meanwhile, MCE (Magnetocaloric effect) is thermal response from material due to external magnetic field. In this work, we focus only on the electrical properties of La_(0.7)Ba0.297Ca0.003MnO_3 (low doped calcium content in the La_(0.7)Ba_(0.3)MnO_3 material) obtained by low temperature sol-gel synthesis. The X-ray diffraction pattern shows that the material is fully crystalline with a rhombohedral structure and R-3c space group. Polycrystalline La_(0.7)B_(a0.297)Ca_(0.003)MnO_3 has magnetic transition behavior from metallic-ferromagnetic behavior to the insulator-paramagnetic behavior with increasing temperature. This material also has magnetoresistance effect. Magnetoresistance value of the material is about 9% at 280 K under an external magnetic field of 1.5 T. In this case, extrinsic MR (extrinsic magnetoresistance) plays an important role since the material is polycrystalline. From this study, we conclude that with low temperature processing we obtained material that has CMR effect and magnetic transition phenomenon like material which prepared by high temperature processing.