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

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

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 abstract Magnetically 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.