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Scanning Probe Microscopy Laboratory

Mount Holyoke College

Katherine Aidala

Clare Boothe Luce

Assistant Professor of Physics

211 Kendade

Mount Holyoke College

50 College St

South Hadley, MA 01075

Phone: (413) 538 2234

Email: kaidala@mtholyoke.edu

 

 

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Ferromagnetic Nanorings 

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.


Control over the chirality (CW or CCW direction) has proven challenging with uniform external fields. The project 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.

 

Nanoring shows different magnetic states with in-plane or circular applied field

   

Cobalt Nanoring (CoNR)

Figure on Right side: AFM topography (left) and MFM (middle and right) image of 10nm thick CoNRs with outer diameter ranges from 700-1100nm and width 150nm. MFM image indicates the onion state of CoNRs with magnetic field 90mT applied along vertical direction (UP). Larger rings (1100nm) were very close to each other show coupling of stray field between two adjacent rings, which indicated from low MFM contrast in the image. Other rings show good onion state because they were far enough from each other along polarization direction. 

MFM images of 10nm thin Cobalt Nanorings (CoNR) and their coupling effect

3D AFM images of Fabricated Cobalt Nanorings Outer/Inner diameter 900/500nm