Electric Field Effects on the Ferromagnetism of Dynamically Phase Separated Manganites

材料研究部的这一奖项支持佛罗里达大学的一个项目，研究电场对一类被称为锰氧化物的材料的磁性的影响。锰氧化物可以存在于各种称为铁磁、反铁磁和顺磁的磁相中，甚至可以形成一种相分离的状态，在这种状态下这些磁相共存。首席研究员和他的研究生和本科生研究团队生长锰氧化物晶体薄膜，并控制其相分离状态，形成嵌入反铁磁绝缘基质的纳米到微米级的铁磁区。然后对样品施加外应力和电场，并使用显微镜和中子反射仪等技术测量对铁磁性区域的影响。该项目的一个可能结果是在使用电场时控制磁场，这可能导致数据存储设备的能源消耗减少。由于该项目包括样品制备和测量，年轻科学家接受了广泛的现代实验技术的培训，所获得的专业知识加强了他们未来在工业和学术界的职业选择。技术摘要钙钛矿型锰氧化物(锰氧化物)显示出具有不同电子、磁性和结构特性的竞争相，这可能导致相共存。在高质量的锰氧化物薄膜中，共存相表现出动态和类流体的行为，甚至可以在应变和电场的影响下在固体样品中空间移动。这个项目研究了锰氧化物中的这种类似流体的行为，以及它在利用电场控制材料磁性方面的可能应用。实验的目的是：(1)确定动态相共存状态下铁磁区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)测量电场对磁性能的影响。采用脉冲激光沉积技术制备了高质量的锰氧化物薄膜。然后利用低温传导原子力显微镜、自旋极化中子反射仪、电阻率和磁化强度测量等技术研究了薄膜和所制备的微/纳米结构的局域和体相性质。用密度泛函理论计算模拟了实验结果，并为实验工作提出了新的方向。该项目的结果有望揭示一种产生电场对材料磁性影响的新方法。由于该项目同时包括样品制备和测量，年轻科学家接受了使用广泛的现代实验技术的培训，获得的专业知识增强了他们未来在行业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.