X-ray and Neutron Scattering Studies of Magnetoelectric Multiferroics

* 非技术摘要 * 磁铁广泛应用于现代技术，从重工业应用到信息存储。 铁电体类似于磁铁，但磁场的作用是由电场发挥的（它们具有“电极化”）。 它们还广泛用于各种应用，如致动器和某些类型的存储芯片。 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，并在电子和太阳能利用方面具有未来应用的潜力。 在这个项目中，将研究两种不同类型的多铁性材料，一种基于Mn和Co，另一种基于Bi和Fe。 确定这些材料的第一类的结构和磁性将有助于理解如何使多铁性增强功能特性。 对第二类材料的研究也将有助于实现这一目的，但除此之外，还有望为新型原型电子器件建立设计原则。 作为一个例子，一个模型二极管（一种常见的电子电路元件）的性能可控的施加电压将被设计和研究。 研究生和年轻的科学家将推动这个项目，高中生将通过一个试点纳米技术计划参与。 该项目预计将为未来的电子和太阳能设备提供具有增强性能的材料，并为这一重要领域的年轻科学家提供教育。多铁性材料是磁性和铁电性相结合的材料。 除了它们的科学兴趣，它们在电子学，自旋电子学和光伏器件方面的应用潜力。 本项目研究了两类多铁性材料：（1）Ca（3）MM 'O（6），其中M，M？是3D金属，是由交换伸缩驱动的新型多铁性材料。 这一机制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特性的材料的策略。 (2)BiFeO（3）是迄今为止唯一一种用于模拟室温器件的多铁性材料。 BiFeO（3）的单晶最近才出现。 我们将研究这些晶体的结构和磁性，并探讨磁电耦合的机制。 将培训中子散射技术方面的年轻专家（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，并为这一重要领域培养年轻科学家。

****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.