Giant Physical Response in Multi-scale Inhomogeneous Oxides

该提案侧重于功能氧化物中发现的微观电子/磁性/结构不均匀性，以及这些材料在宏观物理响应中的相应作用，例如磁阻，磁导率，压电常数以及线性和/或非线性光学特性。 理解和控制非均匀性和物理响应之间的相互关系对于开发新的先进电子和磁性器件至关重要。 热力学或量子临界性、软模、无序效应和电子相分离的概念对于理解相空间中相邻相的共存或波动将是重要的。 该计划设想的活动包括几类重要的复合氧化物材料。 第一个主题是磁阻材料领域（如CuIr 2S 4-CuCr 2S 4和（Bi，Sr）MnO 3-（La，Sr）MnO 3），显示电荷有序绝缘相和铁磁金属相之间的竞争以及共存。 其他主题包括增强MPB附近的铁电弛豫体（PMN-PT）和化学压力效应的几何挫折反铁磁体，如ZnCr 2 O 4的压电响应。 我们还将研究隧道磁电阻在多晶薄膜以及双钙钛矿（Ca，Sr，Ba）Fe0.5Mo0.5O3的三层结构。 该项目的成功将主要取决于功能性复合氧化物（或硫属化物）的全面表征以及高质量多晶材料和单晶的制造。 材料合成和经典表征，包括磁输运，磁化率和热力学测量将在罗格斯大学的PI实验室完成。 此外，X射线散射，中子散射，TEM，微波，拉曼和低温STM实验将通过机构间的合作进行。这项研究将在学生的协助下进行，从而为进入工业，政府或学术界的科学/技术职业做好准备。现代电子和磁性器件通常利用材料在暴露于外部参数（例如磁场或电场、压力或光辐射）下时的物理响应。 最近的研究表明，大规模的物理响应，如磁阻，压电，或线性和/或非线性光学响应，可以大大增强材料与微观电子/磁性/结构的不均匀性。 因此，这种在微观不均匀材料中增强的响应可以为未来的技术提供科学基础。 在这个项目中，我们专注于理解以及控制微观不均匀性和宏观物理响应之间的相互关系。 不均匀性可以与各种电荷/自旋/轨道自由度相关联，并且除了静态空间波动之外，还可以伴随动态波动。 我们将主要研究功能，复杂的氧化物和其他硫属化物，表现出各种竞争或相互对立的基态。 该项目的成功将主要取决于材料的全面表征以及高质量多晶材料和单晶的制造。 材料的制造和基本表征将在罗格斯大学首席研究员的实验室进行，而其他更复杂的表征将通过有效的机构间合作进行。 这项研究将与学生一起进行。他们将获得凝聚态物理学和材料科学前沿领域的高级培训，从而为进入科学/技术劳动力做好准备。

This proposal focuses on the microscopic electronic/magnetic/structural inhomogeneity found in functional oxides, and its corresponding roles in the macroscopic physical response of these materials, such as magnetoresistance, magnetic permeability, piezoelectric constants, and linear and/or non-linear optical characteristics. Understanding and controlling the inter-relationship between the inhomogeneity and physical response are of paramount importance for the development of new advanced electronic and magnetic devices. The concepts of thermodynamic or quantum criticality, soft modes, disorder effects and electronic phase separation will be important to understand the coexistence or fluctuations of neighboring phases in phase space. The activities envisioned in this program include a few important classes of complex oxide materials. The first topic is the area of magnetoresistive materials (such as CuIr2S4-CuCr2S4 and also (Bi,Sr)MnO3-(La,Sr)MnO3), showing a competition between, as well as a coexistence of, charge-ordered-insulating and ferromagnetic-metallic phases. Other topics include the enhanced piezoelectric response near MPB of ferroelectric relaxors (PMN-PT) and chemical pressure effects in geometrically frustrated antiferromagnets such as ZnCr2O4. We will also study tunneling magnetoresistance in polycrystalline films as well as a trilayer structure of double perovskite (Ca,Sr,Ba)Fe0.5Mo0.5O3. The success of this project will critically depend on a comprehensive characterization of the functional, complex oxides (or chalcogenides) as well as the fabrication of high-quality polycrystalline materials and single crystals. Materials synthesis and classical characterization including magneto-transport, susceptibility, and thermodynamic measurements will be done in the PI's lab at Rutgers University. In addition, x-ray scattering, neutron scattering, TEM, microwave, Raman, and low-temperature STM experiments will be performed through inter-institutional collaborations. This research will be conducted with the assistance of students who will thereby be prepared for entry into scientific/technological careers in industry, government or academia. %%%Modern electronic and magnetic devices often utilize physical responses of materials when the materials are exposed under external parameters such as magnetic or electric fields, pressure, or optical irradiation. Recent investigation has suggested that the large-scale physical response such as magnetoresistance, piezoelectricity, or linear and/or non-linear optical response can be drastically enhanced in materials with microscopic electronic/magnetic/structural inhomogeneity. Thus, this enhanced response in microscopically inhomogeneous materials can provide the scientific underpinning for future technologies. In this project we focus on understanding as well as controlling the inter-relationship between the microscopic inhomogeneity and macroscopic physical response. The inhomogeneity can be associated with various charge/spin/orbital degrees of freedom, and may accompany dynamic fluctuations, in addition to static spatial fluctuations. We will primarily investigate functional, complex oxides and also other chalcogenides, showing various competing or mutually antagonistic ground states. The success of this project will critically depend on a comprehensive characterization of the materials as well as the fabrication of high-quality polycrystalline materials and single crystals. Fabrication and basic characterization of the materials will be performed in the laboratory of the Principal Investigator at Rutgers University, while other more complex characterization will be performed through functioning inter-institutional collaborations. This research will be conducted with students. They will acquire advanced training in a forefront area of condensed matter physics and materials science and thus prepare them to enter the scientific/technological workforce.