Exploration of Pressure- and Field-Tuned Phenomena and Phases in Mn- and V-based Spinels

非技术摘要“磁响应”材料具有磁性和导电特性，可以通过压力和磁场进行灵敏地调整，并表现出一系列科学上有趣和技术上有用的特性，包括共存的磁和电顺序，磁场诱导的形状和电导率变化，以及应变控制的磁性。 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，以识别和控制在选定的一组磁响应材料中负责磁响应行为的潜在机制。 该项目的目标之一是确定产生磁响应行为的关键物理机制，控制这些机制以创造具有科学和技术意义的新特性，并调查尚未探索的相区域以发现新的，潜在有用的物理特性。 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-为研究生和本科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，向公众和K-12学生传授科学素养和对科学的热情，这些活动突出了所研究材料的兴奋性和该项目中使用的科学技术。技术摘要磁阻材料，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，可以用压力和磁场灵敏地调节，包括自旋螺旋相、电荷有序相、多铁性相和自旋/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，导致重要的压力和磁场调谐行为，这些材料表现出，主要是由于缺乏光谱信息的自旋和晶格动力学的磁挫材料如何改变磁场和压力的函数。 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。 本研究的目标是阐明微观磁结构的变化，负责新的磁响应行为的磁阻挫材料，使用外加磁场和压力来控制不同的磁响应行为，并探索以前未访问的相制度和现象下的高压和磁场的磁响应材料。除了为几个研究生和本科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，旨在让K-12学生和教师接触材料研究的兴奋，并通过与光学相关的演示给中学生。

Non-technical abstract"Magnetically responsive" materials have magnetic and conducting properties that can be sensitively tuned with pressure and magnetic field, and exhibit a range of scientifically interesting and technologically useful properties, including coexisting magnetic and electric orders, magnetic-field-induced shape and conductivity changes, and strain controlled magnetism. 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 magnetically responsive materials. Among the goals of this project are to identify the key physical mechanisms that give rise to magnetically responsive behavior, to control these mechanisms in order to create novel properties of scientific and technological interest, and to investigate as-yet-unexplored phase regions to uncover new, and potentially useful, physical properties. 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 and undergraduate 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.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 as to 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 elucidate the microscopic magnetostructural changes responsible for novel magnetoresponsive behavior in magnetically frustrated materials, to use applied field and pressure to control different magnetoresponsive behaviors, and to explore previously unaccessed phase regimes and phenomena in magnetically responsive materials under high pressures and magnetic fields. In addition to providing diverse technical training to several graduate and undergraduate 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 through optics-related demonstrations to middle schools students.