The Preparation And The Characteristic Study Of (La_1-xBi_x)_2/3Ca_1/3Mn_1-yFe_yO₃

Since the GMR was found in R1-xA x MnO3 at 1989,much more research were focused on it. At the same time it was used for magnetic storage and magnetic transducer.In the last years,many new physics phenomenons was found in it. Manganese perovskites provide an ideal natural laboratory for studying the physics of strongly correlated electronic systems, since they allow many basic interactions to exist and the interactions be varied at will.A detailed study of these materials has been one of the frontiers in condensed-matter physics and material sciences due to potential application of colossal magnetoresistance(CMR)found in these oxides. In this dissertation, we use the optimal hole-doping manganites as the mother material for our study, and doping it with some selected oxides. The transport properties of the compound samples are studied under zero and applied field. The development and the studying level of colossal magnetoresistance oxides is discussed at the first paragraph. Some important theories were introduced: the double exchange, the John-Teller polaron. Then the crystal frame of manganese perovskites is introduced. It is discussed about the result and the study intention at last. The chapter two describe the preparation methods of the sample, for example, the solid state reaction and the sol-gel method. It is introduced about our experiment technics. In chapter three, we bring forth the conductance curve under magnetic field doping samples of La(1-x)2/3Bi2x/3Ca1/3MnO3. In my opinion, it is because of the lone pair electrons of the outer 6s orbit of Bi3+.It will offer electrons which went in for electric current. The small resistance hasn't application worthiness. We will design a new experiment to solve it. In chapter four, the mother material La2/3Ca1/3MnO3 is doped by Fe at the place of B.We can see from the measure curve that the nonconductor-metal change temperature Tp move to higher and the resistance of the temperature largen. It is because of the two cause :the one is that Fe3+ replace Mn3+ which break the rate of Mn3+/Mn4+,the other one is Fe has unferromagnetic. The five chapter introduce the system of La(1-x)2/3Bi2x/3Ca1/3MnO3 which is doped by Fe. We can find from the result that the conduction character is same to the system of La(1-x)2/3Bi2x/3Ca1/3MnO3 and the resistance is improved at the same time. The last is the conclusion of the paper.