Fall 2015 Physics Colloquium
Wednesday, September 9th
The Glover Memorial Lecture
Rush Holt, American Association for the Advancement of Science, Former New Jersey Congressman
Don't miss the chance to chat with one of the only Congressmen with a Ph.D. in physics in the history of Congress! After retiring from politics, Rush Holt became CEO of the AAAS (the world's larges scientific body) - a position he currently holds. His advocacy for science-informed policy is arguable more urgent now than ever.
Tome Hall Library
Lecture - "Advancing Science"
Anita Tuvin Schlechter Auditorium (ATS)
Sponsored by the Clarke Forum for Contemporary Issues and the Glover Memorial Lecture Fund and co-sponsored by the Churchill Fund and the departments of physics and astronomy, policy studies and political science.
Thursday, September 24
Dr. X. M. Cheng, Bryn Mawr
"Probing Nanomagnetism Using Synchrotron X-ray Based Imaging"
Nanomagnetism, a discipline of studying magnetic phenomena unique to structures with dimensions in the submicrometer scale, is a particularly exciting area of research due to its fundamental role in physics as well as its potential technological applications. A great example is the discovery of the giant magnetoresistance (GMR) effect, an effect of spin-dependent scattering in a nanostructured layered composite. The discovery of the GMR effect, which was awarded the 2007 Nobel Prize for Physics, led the way to an explosion of interest in nanoscale magnetic systems that exploit it.
The synchrotron based x-ray photoemission electron microscopy (PEEM), combined with the large resonant x-ray magnetic dichroism (XMCD) effect present at the L edges of transition metals, offers a very powerful tool to image magnetic configurations in magnetic nanostructures with both chemical and magnetic sensitivities. The pulsed nature of synchrotron radiation provides a natural ability to obtain temporal data with a time resolution related to the x-ray pulse width (typically between 50 and 200 ps), thus offering high sensitivity magnetic imaging with very high time resolution.
In this talk, I will present our study of vortex dynamics in magnetic disks using time-resolved PEEM imaging. We have used x-ray PEEM in a pump-probe arrangement to image the response of magnetic vortices in lithography patterned Ni80Fe20 (Permalloy) disks to fast magnetic field pulses. In isolated Permalloy disks, we find a strong dependence of the magnetic vortex core relaxation behavior on the excitation amplitude, indicative of non-linear magnetization dynamics. We also studied vortex dynamics in planar equilateral triangular arrangements of three magnetic disks with varied center-to-center distances. The observed vortex motion including the frequencies of the vortices in the tri-disk arrangements differs from that of an isolated disk of the same dimension.
Monday, October 12
Informal Q&A Session with Priestley recipient Steven Strogatz
Don't miss the chance to chat with a famous mathematician and nonlinear scientist! Steven Strogatz is the author of a number of best-selling books, including "Sync" and "The Joy of X", and he has appeared on NPR's radio lab, given a TED talk, and blogged for the New York Times.
Tome Hall Library, 2nd Floor
Steven Strogatz, Cornell University
Priestley Lecture - "Synchronization in Nature"
Strogatz will discuss spectacular examples of synchronization in nature, from rhythmically flashing fireflies to crowds of pedestrians that inadvertently caused London's Millennium Bridge to wobble on its opening day.
Anita Tuvin Schlecter Auditorium (ATS)
Reception to follow in ATS Lobby
Tuesday, October 13
Steven Strogatz, Cornell University - Priestley recipient
"Small-World Networks in Science and Society"
Tuesday, November 17th
Sigma Pi Sigma Induction Ceremony & Talk
Michelle Edwards '01
Talk Title: TBD
Dinner will follow at 6pm in HUB Social Hall West