Controlling Microstructures and Interfaces in Oxide Thin Films via Electric Field Processing

磁电材料是指外部磁场引起电响应或外部电场引起磁响应的材料。从历史上看，磁电行为很少在技术上得到应用，因为在大多数表现出这种行为的材料中，响应太小。然而，当两种不同的材料--一种对电场响应，另一种对磁场响应--组合成复合材料时，磁电行为要强得多。该奖项支持基础研究，以了解这种复合磁电材料的行为，特别是两种材料之间的界面。除了了解这些材料中的界面外，还将研究一种新的制造方法，该方法通过施加电场来降低制造温度，从而减少界面上的层混合，进一步改善磁电性能。这项研究的成果可以通过高敏感磁场检测、微波过滤器和先进逻辑器件等应用，造福于美国的经济、国防、安全和社会。这项研究涉及多个学科，包括制造、材料科学、复合材料、磁学和铁电。多学科方法将有助于扩大代表不足的群体对研究的参与，并对工程教育产生积极影响。这项研究支持了利用纳米压印光刻技术在磁致伸缩材料和压电材料之间制造具有独特界面结构的异质磁电薄膜复合材料的研究。潜在的假设是，功能行为是由界面应变耦合驱动的，因此控制界面是至关重要的。在这里，通过电场处理同时了解和控制各个相和界面的纳米结构-性能关系，从而促进了异质氧化物多层膜的制备。这项研究涉及加工、结构特性和物理特性之间的显著相互作用和反馈。通过这项研究，将提高对磁性、铁电和磁电材料的科学知识，包括：了解镍、锌、钴和铁的化学计量变化对镍铁氧体的电磁和磁致伸缩性能的作用；了解通过电场处理分别对每一相的结晶、致密化、晶粒生长和织构的影响；创建具有定制界面几何形状的异质多层膜；了解通过常规烧结方法共烧多层膜；以及了解和控制共烧复合材料电场处理过程中化学物种的相互扩散。

A magnetoelectric material is one for which an external magnetic field causes an electric response or an external electric field causes a magnetic response. Historically, magnetoelectric behavior has found few technological applications because the response was too small in most materials showing such behavior. When two different materials - one responsive to an electric field, and another responsive to magnetic field - are combined into a composite material, however, magnetoelectric behavior is much stronger. This award supports fundamental research to understand the behavior of such composite magnetoelectric materials, in particular the interfaces between the two materials. In addition to understanding the interfaces in these materials, a new manufacturing approach will be investigated, which reduces the manufacturing temperature by applying an electric field and thus reduces the mixing of layers across the interfaces, further improving magnetoelectric properties. The results from this research can benefit the U.S. economy, defense, security and society through applications such as highly sensitive magnetic field detection, microwave filters and advanced logic devices. This research involves several disciplines including manufacturing, materials science, composite materials, magnetics, and ferroelectricity. The multi-disciplinary approach will help broaden participation of underrepresented groups in research and positively impact engineering education. This research supports research focused on using nanoimprint lithography to create heterogeneous magnetoelectric thin film composites with unique interface structures between the magnetostrictive and piezoelectric materials. The underlying hypothesis is that the functional behavior is driven by interfacial strain coupling, and thus controlling the interface is critical. Here the manufacturing of heterogeneous oxide multilayers is advanced by understanding and controlling both the nanostructure-properties relationships of the individual phases and the interfaces simultaneously through electric field processing. The research involves significant interplay and feedback between processing, structural properties and physical properties. Through this research, the scientific knowledge of magnetic, ferroelectric and magnetoelectric materials will be advanced, including: an understanding of the role of stoichiometric variations of Ni, Zn, Co and Fe on electromagnetic and magnetostrictive properties of nickel ferrite; an understanding of crystallization, densification, grain growth and texturing of each phase separately via electric field processing; the creation of heterogeneous multilayers with a tailored interface geometry; an understanding of co-firing multilayers via conventional sintering; and understanding and controlling the interdiffusion of chemical species during electric field processing of co-fired composites.