Dynamic pattern of Skyrmions observed
The illustration demonstrates skyrmions in one of their Eigen modes (clockwise). © Yotta Kippe/HZB
Tiny magnetic vortices known as skyrmions form in certain magnetic materials, such as Cu2OSeO3. These skyrmions can be controlled by low-level electrical currents – which could facilitate more energy-efficient data processing. Now a team has succeeded in developing a new technique at the VEKMAG station of BESSY II for precisely measuring these vortices and observing their three different predicted characteristic oscillation modes (Eigen modes).
Cu2OSeO3 is a material with unusual magnetic properties. Magnetic spin vortices known as skyrmions are formed within a certain temperature range when in the presence of a small external magnetic field. Currently, moderately low temperatures of around 60 Kelvin (-213 degrees Celsius) are required to stabilise their phase, but it appears possible to shift this temperature range to room temperature. The exciting thing about skyrmions is that they can be set in motion and controlled very easily, thus offering new opportunities to reduce the energy required for data processing.
Three different Eigenmodes expected
Theoretical work had predicted that it should be possible to use a high-frequency electric field to excite a group of skyrmions in the sample so that their cores will rotate all together, synchronously like a fish swarm, clockwise or counter-clockwise, or alternatively they can even exhibit a “breathing” motion. Now a team has succeeded in measuring the dynamics of these skyrmions in detail using a single-crystal sample of Cu2OSeO3.
First experimental observation at VEKMAG
The team succeeded at BESSY II in combining a spin-resolving method with an external microwave field. „The resonant magnetic scattering technique when combined with magnetic vectorial external fields shows where the spins are located in the lattice and how they are oriented in space, and all these for each elemental spin species that may exist in the specimen“, explains Dr. Florin Radu, at the Helmholtz-Zentrum Berlin (HZB), a physicist who developed and set up the VEKMAG end station in cooperation with partners from the Universität Regensburg, Ruhr University Bochum, and Freie Universität Berlin. The construction and continuing development of the VEKMAG station are supported by the German Federal Ministry of Education and Research (BMBF) and HZB.
Using electric field induced ferromagnetic resonance excitation and recording the x-ray intensity of a so called Bragg peak, the research group demonstrated experimentally for the first time that all three characteristic oscillation modes occur in Cu2OSeO3 – the team observed magnetic skyrmions turning clockwise, counterclockwise, and expanding and contracting ("breathing" mode). Those modes can be switched and turned around by changing the frequency of the microwave field: Each dynamic mode is achieved for a certain frequency, which further depends on the external magnetic field as well as on other intrinsic parameters of the sample. “This is a first step towards phase specific characterization of controlled skyrmion’s gyrational motion”, Radu says.
Phys. Rev. Lett. (2019): Ferromagnetic Resonance with Magnetic Phase Selectivity by Means of Resonant Elastic X-Ray Scattering on a Chiral Magnet; S. Pöllath, A. Aqeel, A. Bauer, C. Luo, H. Ryll, F. Radu, C. Pfleiderer, G. Woltersdorf, and C. H. Back
DOI: 10.1103/PhysRevLett.123.167201
- Catalysis research at HZB gets new facilityAs part of the CatLab project, HZB has acquired a unique facility for measuring the catalytic performance of thin-film catalysts. Built by ILS in Adlershof, it has now been delivered. The facility consists of a total of eight chemical reactors in which catalytic systems can be tested. At over €2.5 million, this is the largest single investment in the CatLab project.
- Protein crystallography at BESSY II: faster, better and more and more automaticMany diseases are linked to malfunctions of proteins in the organism. The three-dimensional architecture of these molecules is often highly complex, but it can provide valuable insights into biological processes and the development of drugs. X-ray diffraction at the MX beamlines of BESSY II can be used to decipher the 3D structure of proteins. To date, more than 5000 structures have been solved at the three MX beamlines. Here, we present a review and an outlook with Manfred Weiss, head of the research group for macromolecular crystallography.
- 5000th protein structure at BESSY II: Starting point for a COVID drugMany proteins have a complex architecture that enables biological functions. Molecules can bind to specific sites on a protein and alter its function. A team at HZB has now investigated the Nsp1 protein, which plays a role in infection with the SARS-CoV-2 virus. They analysed protein crystals, previously mixed with molecules from a fragment library, and discovered a total of 21 candidates as starting points for drug development. At the same time, they also decoded the 5000th structure at BESSY II.