March 10, 2020 - 4:00 pm to 5:00 pm (already occurred)

This event is open to current Amherst College students, faculty and staff (Amherst College ID required).

When the size of a ferromagnetic structure is on the order of a single domain, where all magnetic moments align parallel to one another, fascinating physics can result. Circularly symmetric structures (i.e., disks and rings) can support a “vortex” state in which the moments align circumferentially with a clockwise or counterclockwise circulation. Typical experiments that apply in-plane magnetic fields cannot select between the CW and CCW states. Instead, we locally pass current through the tip of an atomic force microscope to apply a circular field, directly controlling the vortex circulation. Magnetic force microscopy allows us to image the resulting states in disks and rings. Simulations predict novel states with multiple 360-degree domain walls in rings, which we can understand by considering the switching process and the topology of the domain walls. Potential applications in data storage will be discussed.

Contact Info

Alice Simmoneau
(413) 542-2251
image of e-mail address@amherst.edu