Frustration and Spin Fluctuations in Itinerant Magnets

William Marsh Rice University, Houston TX

Investigators

Abstract

NON-TECHNICAL ABSTRACT This project, supported by the Condensed Matter Physics program of the Division of the Materials Research, presents a systematic way to design and discover magnetic materials belonging to a rare class of compounds, those formed with non-magnetic constituents: itinerant magnets. Magnetic materials are ubiquitous in our modern world and they are at the heart of many technologies including memory storage, magnetic resonance imaging (MRIs) etc. While the applications of magnetic materials are clear, our fundamental understanding of their properties remains largely unknown, especially for those magnetic systems formed without known magnetic elements (like iron or rare earths). The understanding of the purely itinerant magnetism limit is inhibited by the scarcity of relevant compounds, which this project seeks to design and synthesize. An added novelty of this approach is the study of effects in itinerant magnets, related to the crystal structure. This proposal supports the training of undergraduate and graduate student researchers in the areas of crystal growth and materials characterization. The PI continues her ongoing outreach initiatives, which include open houses and science demonstrations at local public schools in addition to developing a new "science a la carte" program, aimed at complex science concepts accessible to young students. Technical abstract: This NSF proposal emphasizes experimental investigations of itinerant magnetic systems to explore the role of spin fluctuations and magnetic frustration in compounds without magnetic elements. New discoveries of two itinerant antiferromagnets, together with the only two known ferromagnets without magnetic elements, offer a platform for two main research thrusts: the study of correlations between the dimensionality and spin fluctuations of itinerant magnets, particularly in the quantum critical regime; the development of a new paradigm for frustration in itinerant magnetic systems. This project addresses issues currently at the forefront of condensed matter physics, such as quantum criticality and attendant non-Fermi liquid effects, and also frustration as a new dimension in a generalized phase diagram for quantum criticality. Our program aligns with the imperious societal need for design and discovery of new materials, while training the new generation of crystal growers. The PI continues her program providing hands-on science experience through the lab "open houses" for the public, training high school students and teachers through internships, and by implementing a "science a la carte" program for schools in the Houston area. This program provides science kits in line with the school science curriculum, together with demonstrations by the PI and her students, and handouts, aimed at fostering learning beyond the classroom. 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.