Probing Effects of Pressure, Mixed Valence, and Spin Frustration on Itinerant Magnets

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PART I: NON-TECHNICAL SUMMARYThis project focuses on investigation of itinerant magnets, a unique class of materials used in societally important clean-energy technologies, including electric vehicles, wind turbines, and magnetic refrigerators. Early studies offered understanding of magnetism in simple metals -- iron, cobalt, and nickel. Currently, however, the state of knowledge and theoretical tools available to materials scientists affords insight into magnetic behavior of more complex intermetallic systems, consisting of two or more elements. This project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, will combine advanced theoretical methods with experimental studies of itinerant magnets. Chemical synthesis, applied pressure, and high magnetic fields will be used to trigger changes in magnetic behavior. A detailed analysis of the changes observed will establish how itinerant magnets respond to variations in their crystal and electronic structures. The outcome of these studies will be improved understanding of itinerant magnets for the design of advanced magnetic materials to be used in clean-energy technologies and other applications. The diversity of theoretical and experimental tools employed in this project will provide unique research training for graduate and undergraduate students, who will become proficient in solid state chemistry, materials synthesis and characterization, and quantum-chemical calculations. For broader outreach, the project PI will also organize nationwide undergraduate summer schools in magnetism and magnetic materials.PART II: TECHNICAL SUMMARYItinerant magnetism has been a fascinating area of research in condensed-matter physics for many decades. Currently, however, such magnetic systems are receiving renewed attention from solid-state chemists, due to the broader availability of theoretical tools for investigation of electronic structure and improved insight into peculiarities of chemical bonding in the solid state. This project aims to uncover correlations between the nature of magnetic ordering and chemical bonding in itinerant magnets by exploring the interplay between the crystal and electronic structure and magnetic properties as a function of chemical substitution, applied pressure, or magnetic field. One aspect of the project will focus on complex transition metal pnictides, with an emphasis on effects of pressure and light-induced excitations that may lead to drastic changes in metallic behavior. The project will also investigate behavior of spin-frustrated systems with metallic or strongly covalent bonding. These studies target the next level of complexity in the spin-frustrated systems, where the addition of itinerant magnetic behavior can lead to the discovery of exotic spin textures and unconventional spin dynamics. The proposed research activities will provide versatile training to graduate and undergraduate students in materials synthesis, investigation of structural and magnetic properties, and studies of the electronic band structure. Undergraduate students and students from underrepresented groups will be involved in the project, both as researchers and through participation in national undergraduate summer schools in magnetism and magnetic materials organized by the PI. This project is supported by the Solid State and Materials Chemistry program in the Division of Materials Research.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.