Elucidating Pressure- and Field-Tuned Phases and Multifunctionality in Magnetic Spinels

非技术性摘要“磁响应”材料具有可以通过压力和磁场调节的特性。这些材料表现出一系列科学上有趣和技术上有用的特性。了解这些奇异特性的物理机制不仅在科学上很重要，而且是优化这些材料用于技术应用的必要先决条件。该项目结合了高压，高磁场和可见激光的使用，以识别和控制负责选定材料组中磁响应行为的潜在机制。在这项研究中采用的各种技术，包括使用金刚石砧室技术的高压技术，高磁场和低温方法，光学和激光技术以及材料生长方法，为研究生研究人员提供了出色的培训，用于学术界，工业界或国家实验室的各种职业。 该项目还致力于通过科学公开讲座，中学科学演示和实验室图尔斯，突出了所研究材料的兴奋，以及在该项目中使用的科学技术，在公众和K-12学生中传授科学素养和对科学的热情。 该项目还包括努力增加STEM领域代表性不足的博士的数量和指导;提高博士生的科学交流技能;并为当前的博士生提供有关其职业道路的指导。技术摘要磁阻挫材料，如磁性尖晶石（化学式AB 2X 4），表现出一系列不同的基态相和现象，这些现象可以用压力和磁场敏感地调节，包括自旋螺旋，电荷有序，多铁性和自旋/轨道液相。 尖晶石和其他磁响应材料的特殊可调谐性使它们成为优秀的科学实验室，可以灵敏地控制和研究无数的相和现象。 然而，有有限的微观理解的微观磁结构效应，导致重要的压力和场调谐行为，这些材料表现出，主要是由于缺乏光谱信息，阐明如何磁挫材料的自旋和晶格动力学变化的磁场和压力的函数。 本研究的目的是填补这一重要的空白，在我们的理解，使用非弹性光散射技术来研究自旋和晶格激发的选择磁挫材料，而场和压力调谐通过其不同的阶段。 本研究的目标是澄清在不同的相区域中观察到的竞争相之间的关系，研究尚未探索的相制度和现象在磁阻挫材料作为温度，压力和磁场的函数，并实现具有科学或技术重要性的物质的异国情调的新阶段。这项研究还揭示了有利于增强磁阻挫材料中磁响应磁化率的一般条件;这些信息是控制这些材料用于有用技术应用的必要先决条件。 除了为几名研究生提供多样化的技术培训外，这项研究还将通过实验室图尔斯之旅影响更广泛的社区，目的是让K 12学生和教师接触到材料研究和与中学生光学相关的演示的兴奋;通过努力提高代表性不足的博士生的数量和指导;该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical abstract"Magnetically responsive" materials have properties that can be tuned with pressure and magnetic field. Such materials exhibit a range of scientifically interesting and technologically useful properties. Understanding the physical mechanisms responsible for these exotic properties is not only important scientifically, but is an essential prerequisite to optimizing these materials for use in technological applications. This project combines the use of high pressures, high magnetic fields, and visible laser light to identify and control the underlying mechanisms responsible for magnetically responsive behavior in a select group of materials. The diverse techniques employed in this research, including high-pressure techniques using diamond anvil cell technology, high-magnetic-field and low-temperature methods, optical and laser techniques, and materials growth methods, provide the graduate student researchers outstanding training for a diverse range of careers in academia, industry, or national laboratories. This project is also dedicated to imparting scientific literacy and enthusiasm for science in both the general public and K-12 students, through public lectures on science, middle-school scientific demonstrations, and lab tours that highlight the excitement of the materials studied, and the scientific techniques used in this project. This project also includes efforts to increase the number and mentoring of underrepresented PhDs in STEM fields; to improve scientific communication skills of PhD students; and to provide guidance to current PhD students concerning their career paths.Technical abstractMagnetically frustrated materials, such as the magnetic spinels (chemical formula AB2X4), exhibit a range of diverse ground state phases and phenomena that can be sensitively tuned with pressure and magnetic field, including spin-spiral, charge-ordered, multiferroic, and spin/orbital-liquid phases. The exceptional tunability of the spinels and other magnetically responsive materials make them excellent scientific laboratories in which myriad phases and phenomena can be sensitively controlled and studied. Yet, there is limited microscopic understanding of the microscopic magnetostructural effects that lead to the important pressure- and field-tuned behaviors these materials exhibit, due largely to the absence of spectroscopic information that elucidates how the spin- and lattice-dynamics of magnetically frustrated materials change as functions of magnetic field and pressure. The purpose of this research is to fill this important gap in our understanding by using inelastic light scattering techniques to study the spin- and lattice-excitations of select magnetically frustrated materials while field- and pressure-tuning through their diverse phases. The goals of this research are to clarify the relationship between competing phases observed in different phase regions, to study as-yet-unexplored phase regimes and phenomena in magnetically frustrated materials as functions of temperature, pressure-, and magnetic-field, and to realize exotic new phases of matter that are of scientific or technological importance. This research also sheds light on the general conditions that are conducive to enhancing magnetoresponsive susceptibilities in magnetically frustrated materials; such information is an essential prerequisite to controlling these materials for useful technological applications. In addition to providing diverse technical training to several graduate students, this research will impact the broader community through laboratory tours aimed at exposing K 12 students and teachers to the excitement of materials research and optics-related demonstrations to middle schools students; through efforts to improve the numbers and mentoring of underrepresented PhD students; and through scientific communication skills training of PhD students.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.