Prof. Dr. Markus Münzenberg
Institut für Physik
Telefon +49 3834 420-4780
Telefax: +49 3834 420-4701
What are the limits to control ultrafast dynamics? With our research we want to unify concepts from femtosecond spin dynamics and spintransport on the nanoscale to make use of them in novel spintronic devices ...
Leading to understanding of microscopic processes and novel applications.
- Ultrafast Magnetism and THz Spintronics
- Magnonics and Spincaloritronics
- Topological Insulators
- Mechanics of Bionanosystems
Picosecond spin currents as THz source
Terahertz waves offer numerous applications in ultrafast science. A a new concept for the generation of terahertz waves using spintronic materials can be realized.
In contrast to previous designs, the emitters consist of thin metal films and take advantage of the spin rather than only the charge of the electron. Following this approach, they developed broadband emitters fully covering the 1-to-30-THz range, while at the same time being simple designed and compact. Compact, because it is based on spin-orbit effects on femtosecond time scales converting the spin current into a THz emitting charge current on few nanometer lenght scales.
T. Seifert et al., Efficient metallic spintronic emitters of ultrabroadband terahertz radiation, Nature Photonics 10, 483–488 (2016).
Coherent ultrafast spin-dynamics probed in three dimensional topological insulators
What happens if a Topological Insulator is driven with circularly polarized photons? A Topological Insulator is not a magnetic material, but due to its topological properties spin-currents are connected with their surface states. In our research we could identify the origin of a recently seen coherent spin-signal present at the ultrafast time scale in these materials. It originates from a coherent spin-polarization present at ultrafast time scales …
Coherent ultrafast spin-dynamics probed in three dimensional topological insulators, F. Boschini et al. Scientific Reports 5, 15304 (2015).
All-optical spin manipulation:
Magnetisation switching of FePt nanoparticle recording medium by femtosecond laser pulses
In a collaboration between Universities of Uppsala, Konstanz, Kiel, Madrid and Western Digital, we lifted the mystery of all-optical manipulation of the magnetization of FePt recording media. Today, FePt nanograins are developed, because of their large magnetic anisotropy, resulting in a high thermal stability even for a few nanometer sized grains, arising in their high coercive field of more than 4 Tesla. They are currently developed further for heat assisted magnetic recording. Our collaboration showed that different steps are important, from ab-initio calculations of the light induced magnetization up to the correct thermal description of the spin ensemble. That shows again the complexity of ultrafast magnetization dynamics, and that there is no unique process for describing ultrafast magnetism. Our calculations for each grain entered into a simple rate model that can explain the switching statistics. To date multiple laser pulses are needed to get a decent writing success. With our single shot experiments compared to the calculations, we can make now predictions for the boundary condition for single-shot laser writing of magnetic bits in the future.
R. John, M. Berritta, D. Hinzke, C. Müller, T. Santos, H. Ulrichs, P. Nieves, J. Walowski, R. Mondal, O. Chubykalo-Fesenko, J. McCord, P. M. Oppeneer, U. Nowak, M. Münzenberg, Sci. Rep. 7, 4114 (2017).
Online publication date: 23-Jun-2017.
Wieck drawbridge in nano:
New equipment allows to fabricate three dimensional objects with a resolution of 150nm. As a test object we fabricated the dutch style drawbridge in the fisher village Wieck, a Greifswald local landmark (original on Wiki). The process works with pulsed laser writing by two-photon laser polymerization that allows to shrink the volume of writing a photoresist for pattering nano- and micron sized structures.
On TV, watch the contribution at the NDR news magazine: www.ndr.de