Doped With Rare Earth Manganese Oxide Structure And Field-induced Transport Properties

In this paper, the elementary theory has been analyzed, in the same time, the experiments of the preparing technology, the structure analyzing and the external fields inducement have also been researched, and the research findings have been gained as follows:Selecting oxides and inorganic salts, the perovskite crystals and series of thinfilms La_1-xCa_xMnO3 and La_1-xBa_xMnO₃ with x ranging from 0.2 to 0.5 have been prepared with Sol-gel and PLD methods. Observing by XRD, SET and AFM, the film fabrication is epitaxial growth, and the surface of film with single crystal is smooth.There are two transition points in the resistant-temperature curve of the La_0.7Ca_0.3MnO)3 film fabricated by sol-gel method, and it is the result of the interaction between double exchange and small polarons that play a important role in CMR films. The material resistant-temperature character analyzing and the resistant change effected by the external fields, and in the result of experiment, the different mechanism lies in the film resistant change caused by the photo or magnetic fields,and it is related to the e_g electrons moving and spinning of Mn³⁺ ion.The curve of resistant-temperature character was fitted by the metallic conductance behavior in the low temperature and the small polaron model in high temperature, the material in the low temperature has the character of metal, and below the 230 K, there is a deflection in the curve of resistant-temperature fitted by the small polaron model. The result provide a possibility to use the photo and current induced phenomena of this compound in optical device and electric arena.