X-ray and Neutron Scattering Studies of Magnetoelectric Multiferroics

*非技术摘要*磁体广泛应用于从重工业应用到信息存储的现代技术中。铁电类似于磁铁，但磁场的作用是通过电场(它们具有“电极化”)来起作用的。它们还广泛用于执行器和某些类型的存储芯片等应用中。多铁性材料是磁性和铁电性相结合的材料。它们引起了科学家的兴趣，并具有未来在电子和太阳能利用方面的应用潜力。在本项目中，将研究两类不同类型的多铁体，一类是基于锰和钴的，另一类是基于铋和铁的。确定第一类材料的结构和磁性将有助于理解如何制造具有增强功能性能的多铁性材料。对第二类材料的研究也将有助于这一目的，但此外，预计还将建立新型原型电子设备的设计原则。作为一个例子，将设计和研究一种具有外加电压控制特性的模型二极管(一种常见的电子电路元件)。研究生和年轻科学家将推动这一项目，高中生将通过试点纳米技术计划参与其中。这个项目有望为未来的电子和太阳能设备展示具有增强性能的材料的方法，并在这个重要领域培养年轻的科学家。*技术摘要*多铁性是结合磁性和铁电性的材料。除了对科学感兴趣外，它们还具有在电子学、自旋电子学和光伏器件方面的应用潜力。这个项目致力于两类多铁性：(1)Ca(3)MM‘O(6)，其中M，M？是3D金属，是一种由交换限制驱动的新型多铁体。这一机制预计将导致磁性和铁电性之间的巨大耦合。X射线和中子散射将用于研究这些材料的结构和磁性，目的是确定多铁性的微观机制，并阐明合成具有增强功能性能的材料的策略。(2)BiFeO(3)是目前唯一用于模拟室温器件的多铁性材料。BiFeO(3)的单晶最近才问世。对这些晶体的结构和磁性进行了研究，并探讨了磁电耦合的机理。将培训年轻的中子散射技术专家(研究生和博士后)，帮助满足新的国家中子散射设施的重要需求。该项目预计将为未来的电子和太阳能设备展示具有增强性能的材料的方法，并培养这一重要领域的年轻科学家。

****NON-TECHNICAL ABSTRACT****Magnets are widely used in modern technology, from heavy industrial applications to information storage. Ferroelectrics are similar to magnets, but the role of the magnetic field is played by an electric field (they possess "electric polarization"). They are also widely used in applications, such as actuators and certain types of memory chips. Multiferroics are materials combining magnetism and ferroelectricity. They are of interest to scientists, and hold potential for future applications in electronics and solar energy utilization. In this project, two different classes of multiferroics, one based on Mn and Co, and the other on Bi and Fe, will be studied. Determination of the structural and magnetic properties of the first class of these materials will help understand how to make multiferroics with enhanced functional properties. Studies of the second class of materials will also be useful for that purpose, but in addition are expected to establish design principles for novel prototype electronic devices. As an example, a model diode (a common electronic circuit component) with properties controllable by applied voltage will be designed and investigated. Graduate students and young scientists will drive this project, and high-school students will be involved via a pilot nanotechnology program. This project is expected to show ways towards materials with enhanced properties for future electronic and solar energy devices, and to educate young scientists for this important field.****TECHNICAL ABSTRACT****Multiferroics are materials combining magnetism and ferroelectricity. In addition to their scientific interest, they hold potential for applications in electronics, spintronics, and as photovoltaic devices. This project is devoted to two classes of multiferroics; (1) Ca(3)MM'O(6), where M, M? are 3d metals, are novel multiferroics driven by exchange striction. This mechanism is predicted to give rise to giant coupling between magnetism and ferroelctricity. X-ray and neutron scattering will be used to study structural and magnetic properties of these materials with the goal to determine the microscopic mechanism of multiferroicity, and to elucidate the strategy for synthesis of materials with enhanced functional properties. (2) BiFeO(3) is so far the only multiferroic material utilized in model room-temperature devices. Single crystals of BiFeO(3) have only recently become available. Structural and magnetic properties of these crystals will be studied, and the mechanism of the magnetoelectric coupling investigated. Young specialists in neutron scattering techniques (graduate students and a postdoc) will be trained, helping to meet an important need at the new national neutron scattering facilities. This project is expected to show ways towards materials with enhanced properties for future electronic and solar energy devices, and to educate young scientists for this important field.