摘要LaMnO3室温下是反铁磁绝缘体，近年来因为掺杂LaMnO3体系的庞磁电阻效应（CMR效应）和良好的高温性能而备受科学家的关注。而La-Mn-O系列的钙钛矿还具有良好的催化性能，所以研究钙钛矿LaMnO3对其本身的理解和其应用前景有着重大意义。

本课题中通过固相反应法、X射线衍射技术和第一性原理采用Materialstudio软件研究B位Ir掺杂型钙钛矿LaMn1-xIrxO3（x=0，0。25，0。5，0。75）电性质和磁属性。实验上，首先通过固相反应法来制作试样进行XRD分析并与使用materialstudio8。0软件对试样进行模拟XRD分析来确定试样制作是否成功。在软件模拟计算部分，使用上述软件的castep模块来模拟和计算钙钛矿LaMnO3在各种掺杂和磁结构下的结构、能量、晶格参数和磁矩；并分析其中各参数改变的影响和确立基态。

首先对比了实验所制得样品的XRD与MS软件模拟的XRD，发现主要尖峰的数量与位置大致相似，所以制样是成功的。另外，计算结果表明，钙钛矿LaMnO3是反铁磁结构，而其掺杂型LaMn1-xIrxO3并没有改变这一特征，当它在磁结构为反铁磁的情况下能量最低，根据能量最低原理，LaMn1-xIrxO3也是反铁磁结构。同时因为Ir原子体积大于Mn原子体积所以随着Ir的逐渐掺杂，LaMn1-xIrxO3的晶体结构体积也在变大。分析能带图时可以看出，LaMn1-xIrxO3（x=0，0。25，0。5，0。75）属于直接能隙的绝缘体或半导体，但是观察态密度图时却发现该体系为金属，Ir原子和Mn原子共价性不强，原子间成键力弱且非局域化性质不强。

毕业论文关键词:钙钛矿LaMnO3；Ir元素；B位掺杂；电属性和磁属性

Abstract LaMnO3 is an anti-ferromagnetic insulator at room temperature, and has been closely watched by scientists in recent years for the use of the LaMnO3 system's magnetoresistance (CMR effect) and good high temperature performance。 It also has good catalytic properties, so the study of perovskite LaMnO3 is of great significance to its own understanding and its application prospects。

This topic through solid instead should method, X-ray diffraction technique and primary principle of using Material Studio software research B-site Ir doped perovskite LaMn1-xIrxO3 electrical properties and magnetic properties。 Experiment, first by solid instead should method to make the sample and XRD analysis and the use Material Studio

8。0 software to simulate the XRD analysis was carried out on the sample to determine whether the sample making success。 In software simulation, using castep module of the software to simulate and calculate the perovskite LaMnO3 structure under all  sorts of doping and magnetic structure, energy, lattice parameter and magnetic moment; And analyze the influence and establishment of the base state of each parameter change。

First, comparing the XRD with MS software simulated by the experiment, the number of the main peak is similar to the location, so the sample is successful。 In addition, the results show that the perovskite LaMnO3 is antiferromagnetic structure, to the principle of lowest energy, LaMn1-xIrxO3 antiferromagnetic structure。 At the same time,  because Ir atoms are larger than Mn, the volume of the crystal structure of the LaMn1-xIrxO3 is also increasing as Ir gets mixed up。 Analysis of energy band diagram, you can see that when LaMn1-xIrxO3 belong to the direct energy gap insulators or semiconductor, but observe state density figure but found that this system for the metal, the Ir atoms and atomic covalent with Mn is not strong, The bonding force between the atoms is weak and the localization properties is not strong。

Keywords: LaMnO3; B-site doped; Electrical properties and magnetic; properties

目 录

第一章绪论