Ultrafast optical excitation of magnetic materials causes distinctive dynamics  of great interest for applications and fundamental science. For example,  irradiation of a magnetic thin film by ~100 fsec duration laser pulses can  reverse the direction of the magnetic moment, even in the absence of an external  magnetic field, a phenomenon known as all optical switching (AOS). Many AOS  studies have only observed deterministic switching if the laser pulse  irradiating the sample is circularly polarized. However, in ferrimagnetic GdFeCo  films, reliable and deterministic helicity-independent all-optical “toggle  switching” (HI-AOS) may be observed and has been understood as an ultrafast  thermal effect.1, 2 In this talk, I will present results on  ultrafast all-electronic switching triggered purely by electrical charge  current pulses. We have recently observed toggle switching of GdFeCo in less  than 10 psec using 9 psec electrical pulses3. In related work, we have now  extended single-shot HI-AOS to ferromagnetic materials,4 which also promises to be  applicable to ultrafast electric current switching of ferromagnets. More  recently, we are studying scaling of the required switching current with size of  the magnetic element down to 50 nm dots and smaller. Our goal is to realize  fully integrated devices suitable for on-chip magnetic memory (and perhaps even  logic) that can be switched with current delivered by an on-chip drive  transistor (no laser involved!) with switching speed in the range of  picoseconds, i.e. two orders of magnitude faster than present spin-torque based  spintronics. Further progress towards this ambitious goal will also be  presented.

1    I. Radu, et al., Nature 472, 205  (2011).

2    T. A. Ostler, et al., Nat Commun 3, 666  (2012).

3    Y. Yang, et al., Science Advances 3, E1603117  (2017).

4    J. Gorchon, et al., Applied Physics  Letters 111 (2017).

Biography

Jeffrey  Bokor is the Paul R. Gray Distinguished Professor of Engineering in the  department of Electrical Engineering and Computer Sciences (EECS) at UC  Berkeley, with a joint appointment as Senior Scientist in the Materials Science  Division at Lawrence Berkeley National Laboratory. He also serves as Chair of  the EECS Department. He received the B.S. degree in electrical engineering from  the Massachusetts Institute of Technology in 1975, and the M.S. and Ph.D.  degrees in electrical engineering from Stanford University in 1976 and 1980,  respectively. From 1980 to 1993, he was at AT&T Bell Laboratories where he  did research on a variety of topics in laser science, surface science, advanced  lithography for integrated circuits, as well as semiconductor physics and  technology, and held several management positions. He joined the Berkeley  faculty in 1993. From 2012 to 2017, he served as Associate Dean for Research in  the College of Engineering. His current research activities include  nanomagnetics/spintronics, graphene electronics, nanophotonics, and  nano-electromechanical systems. He is a fellow of IEEE, APS, and OSA.