High Pressure Synthesis of New Magnets, Featuring Diamagnetic Sources of Anisotropy

Permanent magnets are the functional component of electric motors found in numerous renewable energy applications spanning from regenerative brakes to wind turbines. Magnets that generate higher magnetic flux per volume are central to improved energy generation in these applications. Current state-of-the-art permanent magnets rely upon rare-earth elements for magnetic anisotropy. Despite thirty years of research, no conceptual improvements to strategies of developing better permanent magnets have resulted, since rare-earth elements are excellent sources of magnetic anisotropy. To develop a new class of permanent magnets while retaining the properties conferred by rare-earth elements, a fundamentally new approach is required. In this proposal, we hypothesize that by engendering a covalent interaction between two elements, it will be possible interact the two components of a magnetic moment, spin and orbital angular momentum from two separate atoms to form a complete magnetic moment. This counterintuitive approach will require fundamental studies to test relationship between localization of electrons and magnetic coercivity. Herein, we propose the design, synthesis and characterization of a new class of compounds where magnetic materials are built from heavy main group elements and transition metals. These compounds will be accessed through high pressure synthetic techniques designed to isolate metastable phases. Solid-state syntheses commonly proceed via high temperature routes designed to overcome the slow diffusion of atoms across grain boundaries. In such syntheses, elements are reacted together with a significant application of heat in either a crucible or a quartz tube. An alternate approach is to react elements in an arc melter, wherein electric current can heat samples up to thousands of degrees. Owing to the high necessary temperatures, thermodynamic phases are favored in these reactions, not kinetic reaction products. Consequently, large swaths of phase space, including many different stoichiometries and temperatures, remain untouched. In contrast to these approaches, high pressure is a powerful and underutilized synthetic method pioneered largely in the geosciences to study the properties of materials at conditions deep in the Earth. Through the two separate approaches of high-pressure synthesis in diamond anvil cells or the large volume press at the Advanced Photon Source (APS) (Sector 13), Argonne National Laboratory (ANL), we are able to both perform and monitor high-pressure reactions in situ and scale up these reactions for characterization. Application of powder X-ray diffraction (PXRD), Mössbauer spectroscopy or Raman spectroscopy permit monitoring the physical, electronic, and vibrational structures of reaction as it progresses. Indeed, by probing the reactions in situ we will be able to identify multiple phases as they form in a single reaction. This approach is frequently employed in Earth Sciences, for example when applying high pressure to iron metal to understand the structure of the core, yet is highly unusual for synthetic chemistry. We have two broad aims within this proposal: the synthesis of new magnetic phases and the isolation and/or characterization of the exciting new material FeBi2. The proposed research is separated into two sections, decompression studies and characterization of FeBi2 and the proposed synthesis of new materials. With regard to new materials, our target compounds are simply selected as those with the potential for transformative magnetic properties, engendered by combing first row t