Theory of multiferroic materials and their heterostructures

具有耦合电、磁和弹性特性的材料对科学和技术具有极大的兴趣，因为它们能够连接通常彼此独立的效应。多铁性材料是显示这些耦合的主要候选者。它们具有共存的铁性（或反铁性）序，如铁磁性、铁电性和铁弹性。当这些顺序耦合时，电场能够控制磁性和结构相，并且机械应力能够影响磁性和铁电性。多铁性物理学中的“理想材料”是室温下的铁磁-铁电材料。这样的材料还不存在，但它的合成可以开发出一类新的电子设备，例如具有电写入和磁读取操作的磁存储器，其速度和能量效率需要将硬盘驱动器与个人计算机中的处理器集成在一起。这将彻底改变计算机硬件，对当前技术产生重大影响。我的研究计划是将已知材料转化为这种“梦想材料”的第一步。我正在开发的理论工具，以了解在多铁性材料不同的订单之间的耦合，并确定其作为应变和外部电场和磁场的函数的相图。我的目标是对已知的材料提出修改，并将不同的异质结构联合收割机结合起来，使它们在室温下转变为更接近理想的铁磁-铁电状态。

Materials with coupled electric, magnetic, and elastic properties are of great interest to science and technology, because they are able to connect effects that are usually independent of each other. Multiferroic materials are prime candidates for showing these couplings. They have coexisting ferroic (or antiferroic) orders such as ferromagnetism, ferroelectricity, and ferroelasticity. When these orders are coupled, an electric field is able to control magnetic and structural phases, and mechanical stress is able to affect magnetism and ferroelectricity. The "dream material" in multiferroic physics is a ferromagnet-ferroelectric at room temperature. Such a material does not yet exist, but its synthesis could enable the development of a new class of electronic devices, such as magnetic memories with electric-write and magnetic-read operations that have the speed and energy-efficiency required to integrate the hard drive with the processor in personal computers. This would revolutionize computer hardware with major impact in current technology. My research program is the first step towards transforming known materials into this "dream material". I am developing the theoretical tools to understand the coupling between different orders in multiferroic materials, and to determine their phase diagram as a function of strain and external electric and magnetic fields. My goal is to propose modifications to known materials and to combine different ones in heterostructures so that they are transformed into a state that is closer to the dream ferromagnet-ferroelectric at room temperature.**