Regensburg 2016 – scientific programme
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MA: Fachverband Magnetismus
MA 17: Poster Session I
MA 17.51: Poster
Tuesday, March 8, 2016, 09:30–12:30, Poster B1
Observation of an optically induced magnetic vortex glass in an iron thin film — •Tim Eggebrecht1, Marcel Möller2, Jan Gregor Gatzmann2, Nara Rubiano da Silva2, Armin Feist2, Ulrike Martens3, Konrad Samwer1, Markus Münzenberg3, Claus Ropers2, and Sascha Schäfer2 — 1I. Physikalisches Institut, Universität Göttingen — 2IV. Physikalisches Institut, Universität Göttingen — 3Grenz- und Oberflächenphysik, Universität Greifswald
In this work, we show the generation of magnetic defect states in an ultrathin iron/silicon-nitride bilayer after optical excitation with ultrashort laser pulses. Above a well-defined threshold in laser intensity, the initial magnetic ripple structure transforms on micrometer scales into a dense interwoven network of localized vortices and antivortices with glass-like properties.
Magnetic structures are mapped by transmission electron microscopy (TEM) with Lorentz contrast, where out-of-focus imaging conditions give access to the transverse sample magnetization. The electron microscope is modified to allow for in-situ femtosecond laser excitation.
We analyze the vortex-antivortex network structure, its charateristic length scales and discuss the appearance of topologically protected defects in a rapid heating and quenching model. In particular, possible contributions from the Kibble-Zurek mechanism and subsequent vortex-antivortex annihilation pathways are considered.
We acknowledge support by the DFG via SFB 1073/projects A05 and B01.