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Ab initio study of electrons and phonons in multiferroic BiFeO3

多铁性 BiFeO3 中电子和声子的从头算研究

基本信息

批准号：
EP/E019528/1
负责人：
Gyaneshwar Srivastava
金额：
$ 2.04万
依托单位：
UNIVERSITY OF EXETER
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2006
资助国家：
英国
起止时间：
2006 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FE019528%2F1
关键词：
Ab initio study electrons phonons

项目摘要

Multiferroic materials exhibit two or more properties of ferromagnetism (or antiferromagnetism), ferroelectricity (or antiferroelectricity) and ferroelasticity. Such materials can develop electric polarisation when subjected to an external magnetic field, and can develop magnetisation when subjected to an external electric field. The perovskite BiFeO3 is known to be the only material that exhibits multiferroism at room temperature. In single crystal form itis rhombohedrally distorted perovskite with space group R3c, and is ferroelectric and exhibits antiferromagnetic behaviour up to 643 K. Such 'magneto-electric' materials have technological applications as Hall probes, UHF spin-wave oscillators, and can also be employed in potential applications in information storage, in the emerging field of spintronics, and sensors.Several works have recently been done on the study of the structural, electronic and magnetic properties of BiFeO3. In its single crystal rhombohedral phase it shows only small values of ferroelectric polarisation. However, epitaxially grown films with (001)-oriented pseudotetragonal structure shows an order of magnitude higher polarisation. Polarlized Raman scattering method has been employed to examine some phonon modes for the tetragonal phase. However, no systematic studied have emerged on dynamical properties, e.g. mode assignment and full phonon dispersion relations. As a wide range ofphysical properties of solids depend on their lattice dynamical properties, it is important to undertake a systematic study of phonons for the two structural phases (rhombohedral and tetragonal). Due to the presence of localised Fe 3d electronic states, it is further desirable to investigate changes in phonon modes due to electronic effects such as spin polarisation and strong Coulomb repulsion between the localised states.The proposed research is aimed at carrying out ab-inito theoretical and computational studies of the electronic structure and phonon modes in the multiferroic crystal BiFO3. Our work is expected to help experimentalists analyse their Raman scattering measurements.

多铁性材料具有铁磁性（或反铁磁性）、铁电性（或反铁电性）和铁弹性中的两种或多种性质。这样的材料在受到外部磁场时可以产生电极化，并且在受到外部电场时可以产生磁化。钙钛矿BiFeO 3是已知的唯一在室温下表现出多铁性的材料。在单晶形式中，它是菱形畸变的钙钛矿，空间群为R3 c，并且是铁电的，并且在高达643 K的温度下表现出反铁磁行为。这种“磁电”材料具有霍尔探针，超高频自旋波振荡器的技术应用，也可以在信息存储的潜在应用中，在新兴的自旋电子学领域，和sensors.Several工作最近已经完成了对BiFeO 3的结构，电子和磁性的研究。在其单晶菱面体相中，它仅显示出很小的铁电极化值。然而，外延生长的薄膜（001）取向的pseudotetraxite结构显示了一个数量级更高的极化。用偏振拉曼散射方法研究了四元相的一些声子模。然而，对于动力学性质，例如模式分配和全声子色散关系，还没有系统的研究。由于固体的广泛物理性质取决于它们的晶格动力学性质，因此对两种结构相（菱形和四面体）的声子进行系统的研究是很重要的。由于局域Fe 3d电子态的存在，它是进一步希望调查声子模式的变化，由于电子效应，如自旋极化和强烈的库仑排斥之间的局域stations.The拟议的研究旨在进行ab-inito理论和计算研究的电子结构和声子模式的多铁性晶体BiFO 3。我们的工作有望帮助实验工作者分析他们的拉曼散射测量。