Collaborative Proposal: Physics of Ferromagnetic Nanorings in an External Azimuthal Field

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Technical Abstract:This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Ferromagnetic nanorings exhibit unique magnetic states as the dimensions approach the scale of a single magnetic domain. The closed-flux ?vortex? state exists in appropriately sized disks and rings, in which the circular field lines are entirely contained within the structure. The chirality of this vortex has been proposed as the storage bit in a novel memory device, but control over the chirality has proven challenging with uniform external fields. This collaborative project between Mount Holyoke College and the University of Massachusetts, Amherst, directly explores the switching of the vortex state by passing a current through the tip of an atomic force microscope. This current will produce an azimuthal magnetic field that controls the vortex chirality. Simulations predict that azimuthally applied fields result in interesting states beyond the vortex, generating stable 360 degree domain walls, and effects of asymmetry on the magnetic states will be examined. This work will involve the undergraduate women at Mount Holyoke College, as well as post-docs and graduate students, fostering frequent interaction between the two institutions. Furthermore, curricular material on magnetism will be developed and included in established programs with K12 teachers and the nearby Springfield Technical Community College.Non-technical Abstract:This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Nanoscale magnets exhibit unique magnetic states that can be used as novel data storage devices. Computer hard drives presently store information in binary bits of ?1? and ?0? that are encoded in what are effectively little bar magnets with either the north or south pole pointing up. Magnetic nanorings offer a unique state that has no poles, but instead could store the ?1? and ?0? as clockwise or counterclockwise magnetic fields in what is called the ?vortex? state. This collaborative project between Mount Holyoke College (MHC) and the University of Massachusetts, Amherst (UMass), explores the physics of magnetic nanorings. The fabrication facilities and expertise at UMass will be used to make the nanorings. The atomic force microscope at MHC is capable of precisely positioning a tiny wire at the center of a nanoring. Passing a current through the wire creates a magnetic field that allows control over the direction of the circular magnetization, a feat that is difficult to accomplish with traditional techniques. This work will involve the undergraduate women at Mount Holyoke College, as well as post-docs and graduate students, fostering frequent interaction between the two institutions. Furthermore, curricular material on magnetism will be developed and included in established programs with K12 teachers and the nearby Springfield Technical Community College.