SGER: Multiferroic Materials Based on Polymer-Metal Salt Composites

技术综述：本提案描述了一种基于聚合物/金属盐复合材料的新型柔性多铁材料的研究。多铁性材料是一种稀有材料，它同时表现出铁电性(能够保持永久电矩)和铁磁性(能够保持永久磁矩)。复合材料的聚合物部分是基于聚偏二氟乙烯(PVDF)，这是众所周知的铁电材料。加入少量顺磁性盐可提供磁性成分。当金属盐的质量分数小于1%时，复合材料表现出铁磁性。聚合物/离子盐复合材料的这种行为是史无前例的，有望揭示这类材料的新物理和化学。要解决的基本问题包括：这些稀薄自旋系统中的磁耦合机制是什么？聚合是否起到了作用？电矩和磁矩之间的磁电耦合有什么特点？如何通过改变复合材料的化学成分来改变这些特性？新材料将由不同浓度的顺磁性过渡金属盐(包括Cr3+、Mn2+、Fe2+、Fe3+、Co2+和Cu2+)组成。每一种新的复合材料都将通过一套全面的结构、光谱、磁学和电学实验来表征。非技术摘要：新材料的多铁性有望导致与磁电耦合相关的新物理和新类型的应用。可以由多铁性材料构成的器件包括多态存储元件、可重构天线元件、先进传感器、负折射率介质和微型机电执行器。由于复合材料是基于聚合物基质的，因此这些新器件可以是薄膜、柔性或注塑的。除了满足国家的关键需求外，该项目还将通过提供一个高度多学科的项目来加强研究生和本科生教育。这项研究将与汉斯康空军基地的研究人员合作完成，该基地将为参与研究的学生提供接触学术领域以外的科学家和工程师的机会。研究活动的某些方面对高中生来说是可以接受的，因此将从当地高中招募大学预科学生参与，特别强调针对少数族裔和代表性不足的群体。

TECHNICAL SUMMARY:This proposal describes the study of a new class of flexible multiferroic materials based on polymer/metal salt composites. Multiferroics, which are rare materials, simultaneously exhibit ferroelectricity (capable of maintaining a permanent electric moment) and ferromagnetism (capable of maintaining a permanent magnetic moment). The polymer portion of the composite is based on poly(vinylidene difluoride) (PVDF), which is well known to be a ferroelectric material. Adding small amounts of paramagnetic salts provides the magnetic component. When the metal salt is at concentrations less than 1 % by mass the composite material demonstrates ferromagnetism. Such behavior in polymer/ionic salt composites is unprecedented and promises to reveal new physics and chemistry in this class of materials. Fundamental questions to be addressed include: what is the mechanism of magnetic coupling in these dilute spin systems? Does aggregation play a role? What are the characteristics of the magnetoelectric coupling between the electric moment and the magnetic moment? How can these properties be changed by modifying the chemistry of the composite? New materials will be made composed of a variety of paramagnetic transition metal salts (including Cr3+, Mn2+, Fe2+, Fe3+, Co2+, and Cu2+) at several concentrations. Each new composite will be characterized by a comprehensive set of structural, spectroscopic, magnetic, and electrical experiments.NON-TECHNICAL SUMMARY:The multiferroic nature of the new materials is expected to lead to new physics associated with the magnetoelectric coupling and to new types of applications. Devices that could be constructed from multiferroics include multiple-state memory elements, reconfigurable antenna elements, advanced sensors, negative index media, and microelectromechanical actuators. Since the composites are based on a polymer matrix, these new devices can be thin films, flexible, or moldable. In addition to addressing a key national need, the project will enhance graduate and undergraduate education by providing a highly multidisciplinary project. The research will be done in collaboration with researchers at Hanscom Air Force Base, which will provide the participating students exposure to scientists and engineers from outside the academic realm. Certain aspects of the research activities are within reach of high school students so pre-college students will be recruited from local high schools to participate, with a special emphasis on targeting minority and underrepresented groups.