Mesoscopic Spin Mechanics

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Electrons carry charge, magnetic moment, mass, and mechanical angular momentum. Intensive study of the interplay between magnetism and charge transport, or 'spin electronics', has tremendously enriched our fundamental understanding of magnetic materials and enormously expanded the horizons for magnetic devices. An analogous opportunity exists for 'spin mechanics', by way of detailed exploration of the interactions of magnetism and mechanical motion.***Spin Mechanics first was explored a century ago. 2015 is the centennial of key publications demonstrating the intrinsic coupling between magnetism and mechanics. Barnett observed magnetization changes in response to rotation, and Einstein, working with de Haas, measured the converse (in Einstein's only published experiment). Now is the right time for renewed interest in this physics. The time scale of this coupling is a fundamental characteristic of magnetism and has never been measured. The effects increase in significance for smaller structures, as in the case of spin electronics. New physics can occur, potentially including to new ways of controlling magnetism for applications such as information storage, this time using mechanics.***Also key to the timing of this proposal are opportunities to take advantage of great advances in related, enabling technologies. Experimental capabilities for inducing and detecting nanomechanical motion have been revolutionized by the development of on-chip "cavity optomechanics". Displacement of a nanostructure corresponding to a small fraction of the diameter of a proton can now be measured, and nanomechanical motion powerfully driven by optical spring forces. Extremely fast digital measurement electronics, new nanofabrication processes, and desktop supercomputing for numerical design and modeling, all are new capabilities from just the past couple of years.***The nanomechanical approach is complementary to existing, advanced magnetic measurement methods, and has enabled us already to address fundamental questions in magnetism. The work provides excellent training opportunities for highly qualified personnel. Eight talented graduate students completed their studies during the present granting period, and two postdoctoral fellows went on to tenure-track faculty positions. Outcomes from the continuing work will enable new interdisciplinary applications of magnetism in chemistry, biology, geoscience, and space science.