Magnetoelectric Coupling in Low Symmetry Multiferroics

*技术摘要*本项目的目标是探索多铁性材料中同时存在的磁有序和铁电有序的物理基础。材料中多铁有序的发展通常受到晶格对称性的严格约束，晶格对称性决定了磁结构和相关铁电有序的相变性质。然而，在低对称性晶体中，磁性结构和铁电结构的相对方向不受对称性的限制，只由微观相互作用决定。本项目将通过研究钒酸铁的磁性和铁电有序来探索多铁性中的微观相互作用。钒酸铁是一种低对称性材料。这些研究将使用热力学、磁学和电学技术来表征钒酸铁样品的性质，特别是磁电耦合的细节。微观上的相互作用将通过替代掺杂来调节。该项目将支持博士生的教育和培训，以及一些本科和高中学习。这些学生将接受一系列材料科学技术方面的培训，包括样品制备和低温样品表征。除了对这些学生的专门培训外，该项目还包括向该地区的高中生介绍当前的物理研究课题的外展努力，以及对开发新的材料科学硕士课程的贡献。*非技术摘要*具有磁性的材料，如传统的磁盘驱动器，以及具有电性能的材料，如晶体管，都在现代电子设备中扮演着不可或缺的角色。最近，研究人员发现了一种新的材料，它既具有磁性，又具有一种特殊的电特性，称为铁电。这些被称为多铁性的材料为开发全新类型的电子设备提供了潜力，比如可以通过电压脉冲控制的磁存储，或者即使在断电的情况下也能保持信息的非易失性计算机存储器。这个项目将研究这些同时的磁性和电性如何在特定的铁基多铁体中发展。这将使用热力学、磁学和电学测量来实现，所有这些测量都是在非常低的温度下进行的，并通过中子散射研究提供关于磁性的更多细节。该项目将阐明如何控制这些联合的磁性和电性，最终目标是设计出可以整合到消费设备中的材料。除了加深我们对这些多铁性材料的基本了解外，这个项目还将为学生提供重要的培训。一名博士研究生、三名本科生和三名高中生将学习如何在低温下制备材料以及电学和磁学。这个项目将为这些学生提供一个强大的背景，因为他们正在为高级科学研究和技术开发的职业做准备。

****Technical Abstract****The goal of this project is to explore the physical basis for the concurrent magnetic and ferroelectric order that arises in multiferroic materials. The development of multiferroic order in materials is typically very tightly constrained by the symmetry of the lattice, which determines the transformation properties of the magnetic structure and the associated ferroelectric order. However, in low-symmetry crystals, the relative directions of the magnetic and ferroelectric structures are not restricted by symmetry, and expected to be determined only by the microscopic interactions. This project will focus on probing the microscopic interactions in multiferroics by studying the magnetic and ferroelectric order in iron vanadate, which is a low-symmetry material. These studies will use thermodynamic, magnetic, and electrical techniques to characterize the properties of iron vanadate samples, specifically the details of the magnetoelectric coupling. The microscopic interactions will be tuned by substitutional doping. This project will support the education and training of a PhD student, along with a number of undergraduate and high school studies. These students will be trained in a range of materials science techniques, including sample preparation, and sample characterization at low temperatures. Beyond the specialized training for these students, this project also included outreach efforts to introduce area high school students to current physics research topics as well as contributions to the development of a new Master's program in materials science. ****Non-Technical Abstract****Materials having magnetic properties, such has conventional disk drives, and materials having electrical properties, such as transistors, both have integral roles in modern electronic devices. Recently, researchers have identified a new class of materials that have both magnetic properties and a special kind of electrical property called ferroelectricity. These materials, called multiferroics, offer the potential for developing entirely new types of electronic devices, like magnetic storage that can be controlled using voltage pulses, or non-volatile computer memory that will maintain information even with the power switched off. This project will investigate how these simultaneous magnetic and electrical properties develop in a specific iron-based multiferroic. This will be accomplished using thermodynamic, magnetic, and electrical measurements, all at very low temperatures, with additional detail on the magnetic properties provided by neutron scattering studies. This project will clarify how these joint magnetic and electrical properties can be controlled, with the goal of eventually designing materials that can be incorporated into consumer devices. Along with furthering our basic understanding of these multiferroic materials, this project will provide important training for students. One PhD graduate student, three undergraduate students, and three high school students will learn about preparing materials and electrical and magnetic studies at low temperature. This project will provide a strong background for these students as they prepare for careers in advanced scientific research and technology development.