Fri, 10/13/2017 - 3:00pm to 4:00pm
DeMeritt 240
Colloquium
Dr. Peter Fischer, Berkeley Lawrence National Laboratory

X-raying non-trivial spin textures

Abstract: Nanomagnetism research which aims to understand and control magnetic properties and behavior on the nanoscale through proximity and confinement, is currently shifting its focus to emerging phenomena occurring on mesoscopic scales.  New avenues to control magnetic materials open up through enhanced complexity and new functionalities, which can impact the speed, size and energy efficiency of spin driven applications.

Magnetic soft X-ray spectro-microscopies [1] provide unique characterization opportunities to study the statics and dynamics of spin textures in magnetic materials combining X-ray magnetic circular dichroism (X-MCD) as element specific, quantifiable magnetic contrast mechanism with spatial and temporal resolutions down to fundamental magnetic length and time scales.

I will review recent achievements and future opportunities with magnetic x-ray spectro-microscopies, specifically with full-field soft X-ray transmission microscopy and soft x-ray ptychography. Whereas the former uses Fresnel zone plate optics to form an image, the latter retrieves high resolution amplitude and phase contrast images via reconstruction algorithms of oversampled diffraction patterns [2].

Examples will include the static properties and dynamic behavior of magnetic vortex [3,4] and skyrmion [5,6] textures with potential application to novel magnetic logic and storage devices, magnetic x-ray spectromicroscopy of domain walls [7], and approaches to image the 3dim magnetic domain structures in rolled-up thin films with x-ray tomography [8].

This work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division Contract No. DE-AC02-05-CH1123 in the Non-Equilibrium Magnetic Materials Program (MSMAG).

 

[1] P. Fischer and H. Ohldag, Report on Progress in Physics 78 094501 (2015)

[2] X. Shi, et al, Appl Phys Letter 108, 094103 (2016)

[3] R. Streubel, et al. Appl Phys Lett 107 112406 (2015)

[4] M.-Y. Im, et al. Nature Communication 5 5620 (2014)

[5] S. Woo, et al., Nature Materials 15 501 (2016)

[6] S. Woo, et al., Nature Comm 8:15573 (2017)

[7] M.J. Robertson, et al., J Appl Phys 117 17D145 (2015)

[8] A. Fernandez-Pacheco, et al., Nature Comm 8 15756 (2017)

 

Bio:

Dr. Peter Fischer received his PhD in Physics (Dr.rer.nat.) from the Technical University in Munich, Germany in 1993 on pioneering work with X-ray magnetic circular dichroism in rare earth systems and his Habilitation from the University in Würzburg, Germany in 2000 based on his pioneering work on Magnetic Soft X-ray microscopy.

Since 2004 he is with the Materials Sciences Division at Lawrence Berkeley National Laboratory in Berkeley CA. He is Senior Staff Scientist and Principal Investigator in the Non-Equilibrium Magnetic Materials Program and currently also Acting Division Director at MSD. His research program is focused on the use of polarized synchrotron radiation for the study of fundamental problems in magnetism. Since 2014 he is also Adjunct Professor for Physics at the University of California in Santa Cruz.

Dr. Fischer has published more than 190 peer reviewed papers and has given over 280 invited presentations at national and international conferences. He was nominated as Distinguished Lecturer of the IEEE Magnetics Society in 2011. For his achievements of “hitting the 10nm resolution milestone with soft X-ray microscopy” he received the Klaus Halbach Award at the Advanced Light Source in 2010.

Dr. Fischer is Fellow of the APS and IEEE.