Electric Field Effects on the Ferromagnetism of Dynamically Phase Separated Manganites

该奖项来自材料研究部，支持佛罗里达大学的一个项目，研究电场对一类被称为锰矿石的材料的磁性的影响。锰矿石可以存在于铁磁性、反铁磁性和顺磁性的各种磁相中，甚至可以形成这些磁相共存的相分离状态。首席研究员和他的研究生和本科生研究团队培养了锰晶体薄膜，并控制其相分离状态，形成纳米到微米大小的铁磁区域，嵌入在反铁磁绝缘矩阵中。然后，样品受到外部应力和电场的影响，并使用显微镜和中子反射法等技术测量铁磁区域的影响。这个项目的一个可能的结果是利用电场控制磁场，这可能导致降低能耗的数据存储设备。由于该项目包括样品制备和测量，年轻科学家将接受培训，使用广泛的现代实验技术，所获得的专业知识将增强他们未来在工业界和学术界的职业选择。技术摘要：钙钛矿型锰氧化物表现为具有不同电子、磁性和结构性能的竞争相，从而导致相共存。在高质量的锰酸盐薄膜中，共存相在应变和电场的作用下表现出动态的、类流体的行为，甚至可以在固体样品中进行空间移动。本项目研究了这种在锰矿石中的流体状行为，以及它在电场控制材料磁性能方面的可能应用。实验的目的是：(1)确定铁磁区在动态相共存状态下的类流体行为背后的物理机制，从而找到产生这种状态的最佳条件；(2)研究电场、应变和样品几何形状对动态相分离状态的影响；(3)测量电场对磁性质的影响。采用脉冲激光沉积法制备了高质量的锰酸盐薄膜。然后使用低温导电原子力显微镜、自旋极化中子反射仪、电阻率和磁化测量等技术研究薄膜和制造的微/纳米结构的局部和整体特性。利用密度泛函理论计算对实验结果进行了建模，并为实验工作提出了新的方向。这个项目的结果有望揭示一种新的方法来产生电场效应对材料的磁性。由于该项目包括样品制备和测量，年轻科学家将接受培训，使用广泛的现代实验技术，所获得的专业知识将增强他们未来在工业界和学术界的职业选择。

Non-technical AbstractThis award from the Division of Materials Research supports the University of Florida with a project to study the effect of electric fields on the magnetism in a class of materials called manganites. Manganites can exist in various magnetic phases known as ferromagnetic, antiferromagnetic, and paramagnetic and can even form a phase separated state in which these magnetic phases coexist. The principal investigator and his research team of graduate and undergraduate students grow crystalline thin films of manganites and control their phase separated state to form nanometer to micrometer sized ferromagnetic regions embedded in an antiferromagnetic insulating matrix. The samples are then subjected to external stress and electric field and the effect on the ferromagnetic regions is measured using techniques such as microscopy and neutron reflectometry. A possible outcome of this project is the control of the magnetism in using an electric field, which could lead to data storage devices with reduced energy consumption. Since this project includes both sample preparation and measurement, young scientists are trained to use a broad array of modern experimental techniques and the expertise acquired enhances their future career options in both the industry and academe.Technical AbstractPerovskite manganese oxides (manganites) exhibit competing phases with different electronic, magnetic, and structural properties which can result in phase coexistence. In high-quality thin films of manganites the coexistent phases have shown evidence that they behave in a dynamic and fluid-like manner and can even move spatially within the solid sample under the influence of strain and electric field. This project investigates this fluid-like behavior in manganites and its possible application to control the magnetic properties of the material with an electric field. The experiments are designed to: (1) ascertain the physical mechanism behind the fluid-like behavior of the ferromagnetic regions in the dynamic phase coexistence state and hence, find the optimal conditions for producing such a state, (2) investigate the effects of electric field, strain, and sample geometry on the dynamic phase separated state, and (3) measure the effect of an electric field on the magnetic properties. The high-quality thin films of manganites are grown using pulsed laser deposition. The local and bulk properties of the thin films and fabricated micro/nanostructures are then studied using techniques such as low temperature conducting atomic force microscopy, spin-polarized neutron reflectometry, resistivity, and magnetization measurements. Density functional theory calculations are used to model the experimental results and suggest new directions for the experimental efforts. The results of this project are expected to reveal a novel method for generating an electric field effect on the magnetic properties of a material. Since this project includes both sample preparation and measurement, young scientists are trained to use a broad array of modern experimental techniques and the expertise acquired enhances their future career options in both the industry and academe.