CAS: Hard Permanent Magnets Through Molecular Design

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

PART 1: NON-TECHNICAL SUMMARY Magnetism is a scientific concept that penetrates society in myriad aspects of daily life, from the magnets in electric motors, to portable electronics, to scanners for diagnostic medical imaging. With this project, supported by the Solid State and Materials Chemistry Program in NSF’s Division of Materials Research, researchers at the University of California (UC) Berkeley create new magnetic materials whose design is tailored at the atomic level. The research significantly advances our knowledge and understanding of permanent magnet materials, in particular how to synthesize them through molecular design principles. The research could be transformative in that it offers the potential to inform the design and manufacture of new magnets with superior properties relative to the current state-of-the-art. At a more fundamental level, the research has significant impact in the areas of magnetic materials, materials chemistry, and metal–organic frameworks. In addition, many researchers engaged in the disciplines of condensed matter physics, conductive materials, and quantum information science can also benefit from the new insights gained by the research. Beyond these scientific benefits, this project broadly expand its impact by creating educational opportunities for the general public, specifically through the production of educational outreach program branching off an existing collaboration, where graduate students from UC Berkeley produce lessons on magnetic materials for Bay Area elementary school students. This outreach program is intended to reach large numbers of K-12 students that constitute diverse backgrounds. PART 2: TECHNICAL SUMMARY As part of this project, supported by the Solid State and Materials Chemistry Program in NSF’s Division of Materials Research, researchers at UC Berkeley test the hypothesis that the design principles governing magnetic anisotropy in molecules can inform the design of ultrahard permanent magnet materials. Specifically, work from many research groups over the past two decades has uncovered how coordination chemistry can be applied to tailor geometric and electronic structures of molecules with atomic precision, to maximize the single-ion magnetic anisotropy—the fundamental source of the strength, or “hardness”, of a permanent magnet. This project employs these design principles to incorporate selected classes of high-anisotropy molecules—in particular high-performance single-molecule magnets—into metal–organic framework materials. Both transition metal- and lanthanide (Ln)-based molecular building units are pursued, falling into four main classes: (i) mixed-valence Ln2X3 cores with immense coercivity, (ii) low-valent lanthanide complexes with populated 5d orbitals, (iii) two- and three-coordinate transition metal complexes, and (iv) trigonal paddlewheel complexes. To install strong coupling interactions between these high-anisotropy nodes, two synthetic strategies are utilized: (i) high-energy organic linker-based spins and (ii) electron delocalization in mixed-valence materials. The students and postdoctoral researchers who carry out this research receive training in the synthesis of and characterization of framework materials, including sophisticated physical methods such as magnetometry, x-ray diffraction, and Mössbauer spectroscopy. Moreover, these researchers regularly interact with collaborators in other research groups, both at Berkeley and other institutions. This collaborative culture fosters an open and inclusive forum for scientific advancement, and aids in the professional development and teamwork skills of the involved researchers. 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.