【作者】 李海娜；

【导师】 夏正才；

【作者基本信息】 华中科技大学 ， 材料物理与化学， 2009， 硕士

【摘要】 本文主要从强磁场对科学研究的意义以及脉冲强磁场发展现状出发,对磁化测量、电输运测量及其信号处理等方面进行介绍,特别对脉冲强磁场下的磁化测量系统和电输运测量系统进行了较系统的设计。在材料研究方面,运用固相反应法制备了钒酸盐体系化合物,对其电阻随温度的变化进行了测量,同时利用脉冲强磁场实验平台对(La1-xBix)0.67Ca0.33MnO3磁化特性进行了相关研究。论文主要内容如下:第一、介绍了强磁场下科学研究的意义;同时介绍了脉冲强磁场工程技术及其发展的现状;最后简单概述脉冲强磁场装置的基本组成。第二、详细的叙述了脉冲强磁场下磁化测量系统和电输运测量系统的基本原理;研究了磁化测量过程中如何处理在信号传输过程中由于外界的干扰所产生的噪音信号。第三、阐述了陶瓷材料的显微结构特征,介绍了钒酸盐体系化合物的制备和烧结方法。第四、研究了钒酸盐体系化合物的晶体结构以及相应的性质,其中包括绝缘体向金属的转变,自旋引起的G-type向C-type的转变等等。第五、重点研究(La1-xBix)0.67Ca0.33MnO3化合物在脉冲强磁场下磁特性,随着掺杂浓度以及温度的不同,其饱和磁化强表现出不同的变化,同时观察到掺杂浓度越高所引起的磁滞现象越明显。更多还原

【Abstract】 In this paper, the science and technology of the pulsed high magnetic field are introduced. Based on the pulsed high magnetic field and low temperature system, we desigened the magnetization measurement and electrical transport measurement holders. At the same time, a digital filter was developed to deal with this measuring noise problem..Using the designed system, the magnetization characteristics of (La1-xBix)0.67Ca0.33MnO3 was measured. The thesis mainly contains following contents:First of all, an overview of the science and technology of pulsed high magnetic field and the base structure of pulsed high magnetic field was described. Secondly, the basic theory on magnetization measurements and electrical transport measurements were systematic introduced. At the same time, because there are a lot of high-frequency noises mixed into the signals due to the outside interference in the process of signal transmission, a new digital filter was developed.Thirdly, the crystal structure of vanadium and the corresponding properties were studied, including the metal-insulator transition、spin induced G-type to C-type transition and so on.Finally, the magnetic properties of (La1-xBix)0.67Ca0.33MnO3 was measured, the saturated magnetization was changed with magnetic field in different doping level and different temperature, an obvious hysteresis phenomenon was observed in the manganites with higher doping level.更多还原