The Effect of Strain on the Phase Separation and Magnetoelectric Coupling in Manganites

多铁性物质是可以同时磁化（铁磁性）和带电（铁电性）的化合物。这种化合物有望应用于设备，并带来前所未有的数据存储容量。然而，导致这种独特性质的潜在机制尚不清楚，需要在实际设备制造之前解决。这项个人研究者奖支持了一种称为锰矿石的多氧化锰铁化合物家族的研究。锰矿石的性质与其晶体结构密切相关。该项目的主题是量化晶体结构在多铁性锰矿石中所起的作用，并提出设计更适合器件应用的材料的方法。采用激光烧蚀技术制备高质量的锰酸盐薄膜。这些薄膜对应变的响应（晶体结构的变化）将通过测量其电阻和磁性的变化来研究。应变的微观效应将使用诸如能够绘制材料局部磁性的显微镜等技术来研究。由于研究和培训计划包括样品制备和测量，该奖项将有助于培养本科生和研究生在凝聚态物理研究的各个方面，并为他们提供广泛的基础经验，这将增强他们未来在工业界或学术界的职业选择。钙钛矿型锰氧化物（manganites）表现出微米级相分离和多铁性等独特性能，这与其晶体结构密切相关。因此，锰矿石的电、磁性能对应变很敏感。该个人研究者奖支持一项实验计划，该计划直接测量应变对锰矿性质的影响，并通过将结果与理论模型的预测进行比较，确定锰矿中相分离和多铁性的起源。实验结果也有望揭示增强多铁锰矿石中磁电耦合和控制相分离锰矿石纳米级性能的方法。利用脉冲激光沉积技术可以生长出高质量的锰酸盐薄膜。然后薄膜将受到直接的外部应力，使用三点梁弯曲装置来诱导材料中的单轴应变。利用一套互补的局部和整体测量技术，如磁输运、磁化、扫描探针显微镜和中子反射法，薄膜的相图将被映射为应变、磁场、电场和温度的函数。由于研究和培训计划包括样品制备和测量，本科生和研究生将能够学习各种各样的材料和实验技术，这将为他们的学术和工业生涯做好准备。

NON-TECHNICAL ABSTRACTMultiferroics are compounds which can be simultaneously magnetized (areferromagnetic) and electrically charged (are ferroelectric). Suchcompounds hold promise for applications in devices and lead tounprecedented data-storage capacity. However, the underlying mechanismwhich leads to such unique properties is poorly understood and needs to beresolved before practical devices can be fabricated. This individualinvestigator award supports the study of a family of multiferroicmanganese oxide compounds known as manganites. The properties ofmanganites are intimately linked to their crystal structure. The theme ofthis project is to quantify the role played by crystal structure inmultiferroic manganites and suggest methods to design materials bettersuited for device applications. High quality manganite thin films will begrown using laser ablation. These thin films' response to strain (changein the crystal structure) will be studied by measuring the change in theirelectrical resistance and magnetism. The microscopic effect of strain willbe studied using techniques such as a microscope capable of mapping thelocal magnetism of the material. Since the research and training programincludes both sample preparation and measurement, this award will helptrain undergraduate and graduate students in various aspects of condensedmatter physics research and give them a broad based experience, which willenhance their future career options in the industry or academe.TECHNICAL ABSTRACTPerovskite manganese oxides (manganites) display unique properties such asmicrometer scale phase separation and multiferroism, which are intimatelylinked to their crystal structure. Hence, the electrical and magneticproperties of manganites are sensitive to strain. This individualinvestigator award supports an experimental program to directly measurethe effect of strain on the properties of manganites and by comparing theresults to the predictions of theoretical models, determine the origin ofphase separation and multiferroism in manganites. The experimental resultsare also expected to reveal methods of enhancing the magnetoelectriccoupling in multiferroic manganites and controlling the nanoscaleproperties of phase separated manganites. High quality manganite thinfilms will be grown using pulsed laser deposition. The thin films willthen be subjected to direct external stress using a three pointbeam-bending apparatus to induce uniaxial strain in the material. Using acomplementary suite of local and bulk measurement techniques such asmagnetotransport, magnetization, scanning probe microscopy, and neutronreflectometry, the phase diagram of the thin films will be mapped as afunction of strain, magnetic field, electric field, and temperature. Sincethe research and training program includes both sample preparation andmeasurement, undergraduate and graduate students will be able to learnabout a wide variety of materials and experimental techniques, which willprepare them for academic and industrial careers.