DMREF: Search for Magneto-electronic Behavior in Complex Fluoride-based Interfaces

多功能材料引起了人们极大的兴趣，如多铁性材料，它结合了对电场、磁场和应变场的同时响应。潜在的应用包括新型节能电子设备和超快速信息处理设备。迄今为止，大多数已研究的多铁性材料都是复杂的氧化物材料。尽管从这些材料的研究中产生了令人兴奋的基础发现，但它们的多铁性性能还不足以用于实际应用。在这个项目中，研究人员建议系统地研究复杂氟化物材料作为复杂氧化物的替代品，因为氟化物中多铁效应的不同物理来源可能会增强多铁响应。这项研究将包括计算和实验研究人员之间的协同合作。计算工作将预测最可能具有所需多铁性质的材料，实验部分将合成并表征所建议的材料。反过来，实验结果将用于提高计算的准确性，最终将导致新材料设计的有效优化。本项目的目标是寻找和了解氟基磁电多铁性材料的性质。最近的理论研究表明，在ABF3化合物中，铁电性是由a位离子位移引起的，而不是由磁性b位引起的，这应该会增强磁响应。这与许多复杂的氧化物形成对比，在这些氧化物中，磁性离子位置发生位移，同时往往会削弱磁性。此外，氟离子可以导致反铁磁结构中的大倾斜，再次增强磁电响应。也有迹象表明，复合氟化物与其他氟化物或氧化物之间的界面应具有大而新颖的磁电响应。在本项目中，将使用从头算方法研究复杂氟化物和异质结构的性质，并通过分子束外延合成最有前途的材料，并使用扫描探针和光学技术对其进行表征。实验结果将用于改进计算模型中使用的近似。这种理论-实验的联合努力将有效地识别最可能的界面和具有理想磁电特性的材料，从而大大减少评估大量可能的候选材料所需的时间。

NON-TECHNICAL SUMMARYThere is significant interest in multifunctional materials, such as multiferroics, which combine simultaneous responses to electric, magnetic, and strain fields. Potential applications include new power efficient electronics and ultra-fast information processing devices. To date, most of the multiferroics that have been studied are complex oxide materials. Despite the exciting fundamental discoveries emanating from research on these materials, their multiferroic performance is not yet adequate for use in practical applications. In this project, the investigators propose to systematically study complex fluoride materials as alternatives to complex oxides because the different physical origins of the multiferroic effects in fluorides can potentially enhance the multiferroic response. The research will consist of a synergistic collaboration between computational and experimental researchers. The computational effort will predict the most likely materials to have desired multiferroic properties, and the experimental portion will synthesize and characterize the suggested materials. In turn, the experimental results will be used to improve the accuracy of the calculations, which ultimately will lead to an efficient optimization of the design of the new materials.TECHNICAL SUMMARYThe goal of this project is to search for and understand the properties of fluoride-based magnetoelectric multiferroic materials. Recent theoretical work suggests that in ABF3 compounds, ferroelectricity results from the A-site ionic displacement, and not from the magnetic B-site, which should enhance the magnetic response. This is in contrast to many complex oxides, where it is the magnetic ion site that undergoes the displacement, which at the same time tends to weaken the magnetic properties. Moreover, the fluorine ions can lead to large canting in antiferromagnetic structures, again enhancing the magnetoelectric response. There are also indications that interfaces between complex fluorides and other fluorides or oxides should have large and novel magnetoelectric responses. In this project, the properties of complex fluoride compounds and heterostructures will be studied using ab-initio computational techniques, and the most promising materials will be synthesized via molecular beam epitaxy and characterized using scanning probe and optical techniques. The experimental results will be used to improve the approximations used in the computational models. This joint theoretical-experimental effort will efficiently identify the most likely interfaces and materials which have desirable magnetoelectric properties, thus significantly reducing the time necessary for evaluating the vast number of possible material candidates.