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The Effect of MgO and Nd2O3 Doping on the Electric-Magneto Transport Properties and Magnetoresistance in LCMO System

Author: BaoXiChang
Tutor: XiongYongHong；XiongCaoShui
School: Huazhong University of Science and Technology
Course: Materials Physics and Chemistry
Keywords: Perovskite-type manganese oxide materials Solid state reaction method Low-field magnetoresistance Metal - semiconductor transition Electromagnetic transport behavior Spin-dependent theory Grain boundary effect
CLC: O482.5
Type: Master's thesis
Year: 2007
Downloads: 27
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Abstract


Ever since found large magnetoresistance effect in the perovskite-type manganese oxides, aroused great interest of researchers, but the acquisition of CMR requires a lot of external magnetic field, limiting its application. Therefore, the study of the low-field magnetoresistance has become a hot spot. In this thesis, preferred doped perovskite-type manganese oxides as the population, with the different substances, some oxide composite, these composite samples the electrical transport in the field under the zero field and processing behavior and low field magnetoresistance effect. The text is divided into five chapters: the first chapter of the progress of the perovskite-type manganese oxide, theory and research purpose and content of the paper. The second chapter describes the impact factors of the sample preparation method and sintering process, briefly describes the analysis and testing technology and the matrix material samples prepared basic performance analysis. Chapter La 0.7 Ca 0.3 MnO 3 (LCMO) and MgO composite samples were prepared. Composite samples in the low-field (~ 0.3T) below T LT; TP large magnetoresistance effect, the analysis showed that: Composite samples occur when the temperature is less than TP large magnetic resistance is a non-intrinsic magnetoresistance effect. Intrinsic magnetoresistance effect can be explained by the double exchange interaction between Mn ions in the manganese-based oxide, and this the intrinsic magnetoresistance effect is due MgO relevant layer at the the LCMO particle surfaces of coated caused spin-dependent scattering of the conduction electrons are caused. LCMO the intrinsic peak of MgO sensitive characteristics, the introduction of MgO and its intrinsic peak rapid weakening is a platform, the resistivity of the system increase. The experimental results show that, of MgO particles only enter into LCMO grain boundary bit, no change LCMO the structure, role play the dilution of the magnetic particles in the system, so σS constantly smaller than the saturation magnetization, the TC has not changed. Chapter oxide change as Nd 2 O 3 . Doped with LCMO ash reaches a certain level, the sample resistance temperature characteristics exhibit a bimodal characteristics, the magnetic resistance also appears doublet phenomenon. And transport properties of resistance occurred great changes in the law, these phenomena from the dual-channel models, and new impact to explain the double exchange interaction. And Nd the 2 O 3 intrinsic transport of LCMO MgO so obvious. For the low field magnetic resistance, Nd 2 O 3 the introduction of the particle's spin led to the the LCMO grain boundary bits disordered increase, under a low applied magnetic field is applied, spin disorder of the relevant layer of the particle surfaces can be suppressed, and thus appear to differ from the intrinsic CMR magnetoresistance peak. The fifth chapter is the conclusion.

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CLC: > Mathematical sciences and chemical > Physics > Solid State Physics > Solid nature of the > Magnetic properties
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