RUI: Pressure And Chemical Modulation Of Nanoscale Magnetic Interactions In Metal-Organic Polymers

*非技术摘要*超导体是一种导电材料，它的导电不会因电阻而产生任何损失，它有可能改变我们未来社会的能源需求。然而，科学家们需要提高超导体的工作温度，才能使它们有用。尽管有很多研究，但在许多情况下，超导行为背后的机制仍然是一个谜。为了更好地了解它们的复杂行为，该奖项支持了一个旨在合成和表征分子材料的项目，该材料模仿氧化物和磷酸盐超导体的磁性，这两类超导体可能在更高的温度下工作。直接研究这类系统的挑战在于它们所包含的磁位之间存在着巨大的磁相互作用。通过各种化学方法，将试图通过使用特定的化学键组合控制模型化合物的分子组装来减少这些相互作用的规模。这种结构控制将使一种系统的方法能够改变原子之间的距离、磁活性电子的数量和材料的其他性质。施加压力可能会导致其他不同寻常的发现。材料发现工作将得到广泛的表征和理论工作的补充。这个项目的高度协作性利用了几个国内和国际用户设施，并将为本科生提供独特的机会，让他们前往这些设施参加实验，以及参加专业会议。本科生参与项目的方方面面会对学生产生激励作用吗？这有助于青年科学家的成长和热情，并为他们将来开始研究生工作或继续从事物理科学事业提供必要的背景知识。这项研究项目得到了材料研究部和化学部的支持。*技术摘要*该奖项授予一个以本科生为主的研究所，将支持专注于低维(一维和二维)量子磁体，特别是方形晶格的设计、合成和表征的研究，因为它们可能模仿类似的铜酸盐和铁磷酸盐超导体的结构和磁性。利用配位共价键和强氢键的特定组合，将控制和调节组分的分子位置，并系统地改变层内(J)和层间(J‘)磁相互作用的大小/符号及其相对比(J’/J)。通过(A)离子交换(正或负)、(B)化学掺杂、(C)施加流体静压或化学压力(即同位素取代)和(D)共配体变化来实现体系的磁性可调谐。层间和层内耦合的控制将使得能够调制交换各向异性、临界温度(TN)和临界磁场(BC)。此外，这些系统中的单离子各向异性将通过改变自旋量子数来操纵。材料发现工作将得到广泛的表征和理论工作的补充。磁场和/或压力引起的量子临界性可能导致不寻常的相，使得行为的突然变化可能由于最终驱动相变的磁系统中的不稳定性而发生。本科生参与该项目的各个方面将刺激他们作为年轻科学家的成长和热情，并为他们提供必要的背景知识，以便开始未来的研究生工作或继续从事物理科学的职业生涯。这项研究项目得到了材料研究部和化学部的支持。

****NON-TECHNICAL ABSTRACT****Superconductors, materials which conduct electricity without any loss due to resistance, have the potential to revolutionize the energy demands of our society in the future. However, scientists need to increase the working temperatures of the superconductors in order for them to be useful. Despite much study, in many instances the mechanism behind the superconducting behavior remains a mystery. In an attempt to develop a better understanding of their complex behaviors, this award supports a project aiming to synthesize and characterize molecular materials that mimic the magnetic properties of oxide and pnictide superconductors, two classes of superconductors that may work at higher temperatures. The challenge in directly studying such systems lies in the large magnetic interactions that exist between the magnetic sites they contained. Through a variety of chemical methods, attempts will be made to reduce the scale of these interactions by controlling the molecular assembly of model compounds using particular combinations of chemical bonds. This structural control will enable a systematic approach to vary distances between atoms, the number of magnetically-active electrons, and other properties of the material. The application of pressure may lead to other unusual discoveries. The materials discovery effort will be complemented by extensive characterization and theoretical work. The highly collaborative nature of this project makes use of several national and international user facilities and will provide unique opportunities for the undergraduate students to travel to facilities to participate in the experiments, as well as to attend professional conferences. Undergraduate student involvement in every aspect of the project will stimulate the students? growth and enthusiasm as young scientists, as well as provide them with the necessary background to begin graduate work in the future or to go on to careers in the physical sciences. This research project receives support from the Division of Materials Research and the Chemistry Division.****TECHNICAL ABSTRACT****This award to a Predominately Undergraduate Institution will support research focusing on the design, synthesis, and characterization of low-dimensional (1- and 2D) quantum magnets, in particular square lattices, as they may mimic the structural and magnetic properties of analogous cuprate and iron-pnictide superconductors. Using specific combinations of coordinate covalent bonds and strong hydrogen bonds, the molecular positioning of components will be controlled and tuned and the magnitude/sign of the intralayer (J) and interlayer (J') magnetic interactions and their relative ratio (J'/J) will be systematically varied. The magnetic tunability of the systems will be achieved by: (a) ion-exchange (either positive or negative), (b) chemical doping, (c) application of hydrostatic or chemical pressure (i.e., isotopic substitution) and (d) co-ligand variation. Control of inter- and intralayer couplings will enable the modulation of the exchange anisotropy, critical temperatures (TN), and critical magnetic fields (Bc). In addition, the single-ion anisotropy in these systems will be manipulated by modifying the spin quantum number. The materials discovery effort will be complemented by extensive characterization and theoretical work. Magnetic-field and/or pressure-induced quantum criticality may lead to unusual phases, such that abrupt changes in behavior can occur due to instabilities in the magnetic system which ultimately drive phase transitions. Undergraduate student involvement in every facet of the project will stimulate their growth and enthusiasm as young scientists, as well as provide them with the necessary background to begin graduate work in the future or to go on to careers in the physical sciences. This research project receives support from the Division of Materials Research and the Chemistry Division.