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Calendar: ALS Calendar
Title: ALS-CXRO Seminar Series | Vojtěch Uhlíř
When: 05/15/2013 3:00 PM - 4:00 PM
Description: ALS/CXRO Seminar Series

Wed, May 15, 2013
15-253 Conf Rm

Peter Fischer/Jinghua Guo

Presented by:
Vojtěch Uhlíř
UC San Diego

Dynamic switching of the spin circulation in
tapered magnetic nanodisks

Magnetic vortices are curling magnetization structures which represent the lowest energy state in submicron-sized magnetic disks or polygons. Magnetic vortices are characterized by the sense of in-plane magnetization circulation and by the polarity of the vortex core. With each having two possible states, there are four possible stable magnetization configurations that can be utilized for a multibit memory cell. Dynamic control
of vortex core polarity has been demonstrated using both alternating and pulsed magnetic fields and currents. However, until now, control of spin circulation in magnetic vortices has only been demonstrated experimentally under static conditions.

Field-induced circulation switching requires removing the vortex core out of the disk and then reforming the vortex with opposite circulation. This can be achieved by using a static magnetic field and exploiting a geometric asymmetry in the object. Scaling this process down in time, using nanosecond and shorter magnetic field pulses, necessarily introduces complex magnetization dynamics that might prevent efficient and reproducible switching of the spin circulation.

We will show that these issues can be overcome by selecting magnetic disks of an appropriate geometry and demonstrate controlled switching of spin circulation using nanosecond field pulses by imaging the process with full-field soft X-ray transmission microscopy. The dynamic reversal process is controlled by far-from-equilibrium gyrotropic precession of the vortex core, and the reversal is achieved at significantly reduced field
amplitudes when compared to static switching.

Work performed in collaboration with M. Urbánek, L. Hladík, J. Spousta and T. Šikola (CEITEC, Brno, Czech Republic), M.-Y. Im and P. Fischer (CXRO, LBNL), N. Eibagi, J. J. Kan and E. E. Fullerton (UCSD).

Vojtěch Uhlíř is a Postdoctoral Researcher in the Center for Magnetic Recording Research, University of Califonia, San Diego. He received his M.Eng degree (2006) in Physical Engineering from Brno University of Technology, the Czech Republic and a Ph.D. (2010) in Physics from University of Grenoble, France and in Physical and Materials Engineering from Brno University of Technology. His primary research interests are in magnetic thin films and nanostructures, magnetization dynamics and spintronics.
Location: 15-253-CR(80)