Discovery of Complex Spin Textures via Magnetic Phase Boundary Mapping

NON-TECHNICAL SUMMARY Itinerant (metallic) magnets are a unique class of magnetic materials. Such materials, especially ones that are not simply ferromagnetic or antiferromagnetic, are increasingly important for modern technologies. Applications include quantum information science, data storage and next-generation energy-efficient technologies, for example spintronic devices, electric vehicles, and magnetic refrigerators. With this project, supported by the Solid State and Materials Chemistry Program and the Condensed Matter Physics Program, both in NSF’s Materials Research A Section, Professor Michael Shatruk and his team at the Florida State University (FSU) use chemical approaches and various external physical stimuli to deliberately create complex spin textures in metallic crystals. They arrange atomic spins (the origin of magnetism) in helices, spirals and vortices instead of rectangular structures. By rationally designing materials with novel magnetic properties, they lay the foundation for the technologies mentioned above and for yet to be discovered phenomena. Because it is interdisciplinary, bridging chemistry and physics, this project provides unique research training for graduate and undergraduate students. Additionally, the principal investigator offers research experiences to high school students through his Materials Innovation aNd Discovery Lab (MINDLab) program. All these activities help prepare the next-generation STEM workforce for materials industry and education. TECHNICAL SUMMARY The intimate coupling between magnetic ordering and electronic structure makes itinerant magnets a fertile playground for the discovery of complex, potentially topological magnetism. This project, supported by the Solid State and Materials Chemistry Program and the Condensed Matter Physics Program in NSF’s Materials Research A Section, develops Magnetic Phase Boundary Mapping (MPBM) - the systematic interrogation of the parameter space that separates competing collinear magnetic structures - as a rational route to the discovery of intermetallics that exhibit non-collinear spin textures. Building on prior results, the project applies MPBM to three classes of metallic systems in which competition between magnetically ordered states, coupled to structural phase transitions or electronic instabilities, can stabilize non-collinear order: kagome-lattice metals AM6Ge6, half-Heusler alloys and related ABX intermetallics, and intercalated metallic ditellurides MTe2. Candidate phase boundaries are identified through density-functional-theory analysis and probed experimentally by variable-temperature and high-pressure diffraction, magnetometry, neutron scattering, X-ray absorption and magnetic circular dichroism spectroscopies, angle-resolved photoemission, and Mössbauer spectroscopy. The project utilizes advanced large-scale research facilities at national labs for to determine magnetic structures and detailed structure-property correlations. The research activities provide interdisciplinary training to graduate and undergraduate students in materials synthesis, investigation of structural and magnetic properties, the use of neutron scattering methods, and studies of the electronic band structure, thus educating the next generation of workforce for materials research and enterprise. The principal investigator and his team contribute to broad educational efforts through nationwide undergraduate summer schools in magnetism and magnetic materials, the MINDLab research experiences aimed at high school students, and outreach activities connected to the FSU Quantum Initiative. 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.