Effect of Complex Addition on the Electrical Transport and Magnetoresistance Properties of La2/3(Ca0.65Ba0.35)1/3MnO3

Effect of Complex Addition on the Electrical Transport and Magnetoresistance Properties of La2/3(Ca0.65Ba0.35)1/3MnO3
　　Manganese oxides with peroveskite structure have been the subject of intense study in recent years due to the complex in teraction between electrons,lattices and spins.Specially,the potential technological application related to the colossal manganetoresistance (CMR) effect has activated the interesting on the materials.However,for a single crystal of a pure Ball Neodymium Magnets manganese oxide, the intrinsic CMR can be observed only at a high magnetic field(several Teslas) and in a narrow temperature window near Curie temperature. For a crystalline, although a higher magnetoresistance was observed at a lower magnetic field in the temperature much lower than the Curie temperature, the low field magnetoresistance decreased rapidly with increasing in the temperature.
　　Thus, there are many technological problems as the manganese oxides were used to the electronic devices.The material which has the structure "FM/ML/FM" shows the low field MR(LFMR),where FM and ML represents the ferromagnetic metal and middle layer,respectively.So,we try to optimize the structure to enhance the LFMR and the sensitivity to the magnetic feld.For the ferromagnetic metals,MR is higher with the higher spin polarization.so we try to bring Ti、Cu into the A site、B site or grain- boundaries of La2/3(Ca0.65Ba0.35)1/3MnO3(short LCBMO), changing the its electric and magnetic properties,to enhance the MR.In this thesis,our main investigation including:(l)A summary of the formation and its physical problems of the structure, properties and magnetoresistanee in the manganese oxides has been given. We summarize the research work related to the FM/ML/FM material,and the fu ndamental of theory and experiment of the thesis has put forward on the basis of it .(2) The influences of diferent preparation procedures are compared and optimal two are chosen.We use the Glycine-nitrate process and sol-gel to produce the manganese oxides.
　　The electric, magnetic properties and magnetoresistance of LCBMO are investigated.(3) For the different preparation procedures of LCBMO,we observed hat sintering temperature evidently affectes the results by changing the grain size of LCBMO,the http://www.chinamagnets.biz/ larger and smaller size both go against the effect.(4) Glycine-nitrate process (GNP) synthesized La2/3(Ca0.65Ba0.35)1/3MnO3 /xTiO2 and La2/3(Ca0.65Ba0.35)1/3MnO3/0.035TiO2/xCuO system, Effects of complex addition on the electrical transport and magnetoresistance properties of La2/3(Ca0.65Ba0.35)1/3MnO3 are studied. A composite containing (LCBMO) and Cu dependent material is investigated.Compared to LCMO, the composite has a lower insulator-metal transition temperature(Tp) and a substantial reduction in the resistivity over the whole temperature range studied.