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

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

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 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 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.