pd填隙和化學(xué)鍍pd對(duì)la,0.7ca,0.2sr,0.1mno,3電磁輸運(yùn)特性的影響

1、華中科技大學(xué)碩士學(xué)位論文Pd填隙和化學(xué)鍍Pd對(duì)LaCaSrMnO電磁輸運(yùn)特性的影響姓名：胡海鑫申請(qǐng)學(xué)位級(jí)別：碩士專業(yè)：材料物理與化學(xué)指導(dǎo)教師：熊曹水;熊永紅20090602華 中 科 技 大 學(xué) 碩 士 學(xué) 位 論 文 IIABSTRACT We have investigated the effect of Pd addition LCSMO prepared by solid state reaction method, and s

2、tudied systematically the effects of Pd addition LCSMO on the structure, magnetic, electric and magnetoresistant properties. And the possible mechanisms of these characters were discussed. Moreover, we have attempted to

3、prepare LCSMO/Pd composites in electroless plating method. We hope we could get some meanful results by comparing the CMR composites prepared in these two methods. The dissertation consists of five chapters: The first ch

4、apter mainly introduces some theories of the manganese oxides and research progress. Also, the application status is also referred. The research intention and significance of this thesis were put forward on the basis of

5、the introduction. The second chapter mainly discusses some synthesis methods, including solid state reaction and electroless plating method. The pre-treatment process of ceramic powders and progress of researchare and si

6、mply introduced. In chapter three, we select LCSMO as the matrix material and introduce metal Pd phase into LCSMO matrix by conventional solid-state reaction method. Pd addition has little influence on the Curie temper

7、ature (Tc), but dramatically decreases the resistivity (ρ) and shifts the metal-insulator transition temperature (Tp) to a higher temperature. The ρ in the ferromagnetic (FM) metallic regime follows an empirical relation

8、, ρ=ρ0+ρ2.5T2.5+ρ7.5T7.5, reflecting that the conductivity mechanism is related to electron-electron, electron-phonon, electron-magnon scattering. In the paramagnetic (PM) insulating region, the ρ data fit well to the ad

9、iabatic small-polaron-hopping model. Moreover, the ρ versus T curves for all samples excellently fit to the phenomenological model derived from spin-polarized tunneling at grain boundaries and thermal activation. Additio

10、nally, a large enhancement of room temperature magnetoresistance (MR), defined as Δρ/ρ(H=0) over 40% and 12% can be obtained at 20kOeand 3kOe, respectively. The good agreement between the field-dependence of MR and the B