掺杂稀土锰氧化物的结构和外场诱导输运特性研究

【作者】 陈钊；

【导师】 陈长乐；

【作者基本信息】 西北工业大学 ， 凝聚态物理， 2005， 硕士

【摘要】 本文从材料制备工艺、结构分析、外场诱导等方面对钙钛矿结构锰氧化合物特大磁电阻材料进行了多方的实验研究和初步的理论分析,取得了以下研究成果: 采用无机途径的溶胶-凝胶法和脉冲激光沉积法制备了具有CMR效应的钙钛矿结构的La_1-xCa_xMnO₃（x=0.2,0.3和0.5）和La_1-xBa_xMnO₃（x=0.25,0.5）系列块材和薄膜。对于薄膜的XRD、SET和AFM分析测试,肯定了制备的薄膜是单晶外延生长的,具有平整的表面。在溶胶-凝胶法制备的La_0.7Ca_0.3MnO₃薄膜的电阻-温度曲线中,出现了两个转变点,这是双交换作用和晶格畸变产生的小极化子相互竞争的结果;进行了电阻-温度特性以及外场作用下材料电阻特性变化的实验,从实验结果中发现,磁场和光照对薄膜电阻的改变存在不同的输运机制,认为这主要是与Mn³⁺离子的e_g电子的运动和自旋排列有关;采用了金属电导行为和小极化子模型进行低温和高温段电阻-温度特性的曲线拟合,低温具有明显的金属行为,而在高温230K以下,开始偏离小极化子模型。更多还原

【Abstract】 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.更多还原