Ferroelectricity Emerging from Antisite Defects in Complex Oxides

非技术描述：铁电材料可以存储电荷，并在能量存储，存储设备和致动器中有应用。该项目开发了一类新的铁电材料，也具有磁性。这些特性的组合使得它们对于低功率存储器和计算设备特别有用。找到在室温下同时具有磁性和铁电性的材料一直是一个挑战，但最近的工作通过操纵一类含有铁和稀土金属的氧化物的组成来实现这一目标。组成的变化产生一种特殊类型的缺陷，这是铁电性的来源。本研究项目研究材料成分中的铁电性，预计将显示出最强的效果。更广泛的影响包括学生培训，促进多样性的活动，通过活动和在线课程进行公众宣传，以及向工业集团转让技术。公共宣传是在纳米天文台，一个年度活动，与会者参观纳米织物和表征实验室在麻省理工学院的纳米技术的演示，并通过免费的在线课程，有助于微未成年人认证提供。通过一个将少数民族的本科生带到麻省理工学院的计划，以及通过部门多样性，公平和包容性合作项目，对服务不足的少数民族进行宣传。技术描述：铁电材料是有用和有趣的材料，在能量存储，记忆和执行器中有应用。此外，当与铁磁或反铁磁序结合时，材料是多铁性的，并表现出额外的功能，如电压诱导的磁化变化或磁场诱导的极化变化。本研究项目探讨了一种假设，即反位缺陷可以在通式为ABO_3的钙钛矿中诱导铁电性，即在一个应该包含不同阳离子的位置上存在一个阳离子。最近的研究表明，在Y：Fe 1的YFeO_3中，反位缺陷导致了强的室温铁电性，即使体化学计量比材料是非铁电性的，并且密度泛函理论预测，这种机制在具有较小稀土阳离子（如Lu）的正铁氧体中会更强。本文研究了富稀土正铁氧体LuFeO_3和YbFeO_3薄膜的反位缺陷介导铁电性，并测量了磁场对其铁电响应的影响。更广泛的影响包括学生培训，促进多样性的活动，通过活动和在线课程进行公众宣传，以及向工业集团转让技术。公共宣传是在纳米天文台，一个年度活动，与会者参观纳米织物和表征实验室在麻省理工学院的纳米技术的演示，并通过免费的在线课程，有助于微未成年人认证提供。通过一个将少数民族的本科生带到麻省理工学院的计划，以及通过部门多样性，公平和包容性合作，对服务不足的少数民族进行了推广。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

Nontechnical Description: Ferroelectric materials can store electric charge, and have applications in energy storage, memory devices, and actuators. This project develops a new class of ferroelectric materials that also have magnetic properties. This combination of properties makes them particularly useful for low power memory and computing devices. It has been a challenge to find materials that possess both magnetic and ferroelectric properties at room temperature, but recent work shows a path to this goal by manipulating the composition of a class of oxides that contain iron and a rare earth metal. The change in composition produces a particular type of defect which is the source of the ferroelectricity. This research project investigates ferroelectricity in material compositions that are predicted to show the strongest effects. Broader impacts include student training, activities to promote diversity, public outreach via events and online classes, and technology transfer to industrial groups. Public outreach is offered at The Nano-Observatory, an annual event where attendees visit a nanofabrication and characterization lab at MIT for demonstrations of nanotechnology, and through free online classes that contribute to a micro-minor certification. Outreach to underserved minorities is carried out through a program that brings undergraduates from minority populations to MIT, and through a departmental Diversity, Equity and Inclusion Collaborative.Technical Description: Ferroelectrics are useful and interesting materials, with applications in energy storage, memory and actuators. Furthermore, when combined with ferro- or antiferromagnetic order, the materials are multiferroic and exhibit additional functionality such as voltage-induced changes in magnetization or magnetic field-induced changes in polarization. This research project explores the hypothesis that ferroelectricity can be induced in perovskites with generic formula ABO_3 as a result of antisite defects, i.e. the presence of one cation on a site that should contain a different cation. Recent work has shown that antisite defects in yttrium orthoferrite YFeO_3 with Y:Fe 1 lead to a robust room-temperature ferroelectricity, even though the bulk stoichiometric material is non-ferroelectric, and density functional theory predicts that this mechanism would be even stronger in orthoferrites with smaller rare earth cations such as Lu. This research investigates antisite-defect-mediated ferroelectricity in thin films of rare earth-rich orthoferrites LuFeO_3 and YbFeO_3, and measures the effect of magnetic field on their ferroelectric response. Broader impacts include student training, activities to promote diversity, public outreach via events and online classes, and technology transfer to industrial groups. Public outreach is offered at The Nano-Observatory, an annual event where attendees visit a nanofabrication and characterization lab at MIT for demonstrations of nanotechnology, and through free online classes that contribute to a micro-minor certification. Outreach to underserved minorities is carried out through a program that brings undergraduates from minority populations to MIT, and through a departmental Diversity, Equity and Inclusion Collaborative.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.