From Dublin to Berlin as a Humboldt Research Fellow
Dr. Katarzyna Siewierska joins the group of Prof. Alexander Föhlisch as a postdoctoral Humboldt Research fellow. © Privat
Dr. Katarzyna Siewierska joins the group of Prof. Alexander Föhlisch as a postdoctoral Humboldt Research fellow. She has earned her PhD at Trinity College in Dublin, Ireland, and plans in the next two years to explore the electronic structure and spin dynamics of half-metallic thin films at BESSY II. Understanding these spintronic materials better may pave the way for more energy efficient data storage technologies.
Katarzyna Siewierska describes her project herself very clearly:
A dream material for spintronics would have low/zero net moment, no stray fields, high resonance frequency, low damping and be 100 % spin polarised, combining the best features of a metallic ferromagnet and an antiferromagnet. Such materials have the potential to revolutionise magnetic data storage and data transfer. They are called zero moment half-metals (ZMHM). This new material class was theoretically predicted in 1995, but it took almost 20 years before the first member, Mn2RuxGa, was demonstrated in 2014.
Up to now, the few other examples of ZMHMs are all Mangan-based Heusler alloys, revealing the critical role of Mangan for obtaining the uniquely desirable combination of properties. It is of great research interest to understand why this is so.
Synchrotron radiation-based techniques provide important insights into the electronic and magnetic properties of spintronic materials due to their sensitivity to spin and crystal structure, coupled with element specificity.
In this work we will combine the expertise of researchers at BESSY II in resonant inelastic X-ray scattering (RIXS) with the high quality ZMHM thin films I fabricated and studied at Trinity College Dublin (TCD) during my thesis. The goal is to confirm the half-metallic band structure of MRG, explore the spin-lattice relaxation and investigating magnon excitations to obtain information about their dispersion and the energy of ferrimagnetic resonance modes.
- HZB-magazine lichtblick - the new issue is out!In the cover story we introduce Astrid Brandt. She is Head of User Coordination at Helmholtz-Zentrum Berlin. She and her team keep constant track of applications, measurement times and publications of the 1000 guest researchers who come to BESSY II each year.
She has always been fascinated by science. But she has also never let go of her other passion, which is music.
- “Germany mustn’t lose sight of its ambitious goals”The Science Year 2025 is dedicated to the topic of ‘Future Energy’ and the Helmholtz Association is conducting cutting-edge research in this field. An interview with Bernd Rech, Vice-President Energy of the Helmholtz Association and Scientific Director at HZB, on topics such as: Where does Germany stand with the restructuring of its energy system? What contribution can research make? And what about hydrogen, nuclear energy and nuclear fusion, and the new challenges for a secure supply in times of cyber attacks?
- Nanoislands on silicon with switchable topological texturesNanostructures with specific electromagnetic patterns promise applications in nanoelectronics and future information technologies. However, it is very challenging to control those patterns. Now, a team at HZB examined a specific class of nanoislands on silicon with interesting chiral, swirling polar textures, which can be stabilised and even reversibly switched by an external electric field.