Spintronics: A new path to room temperature swirling spin textures
The team led by Sergio Valencia analysed the samples with photoemission electron microscopy using XMCD at BESSY II. The images show the radially aligned spin textures in a round and a square sample consisting of a ferromagnetic material on a superconducting YBCO island. The white arrow shows the incident X-ray beam. © HZB
A team at HZB has investigated a new, simple method at BESSY II that can be used to create stable radial magnetic vortices in magnetic thin films.
In some materials, spins form complex magnetic structures within the nanometre and micrometre scale in which the magnetization direction twists and curls along specific directions. Examples of such structures are magnetic bubbles, skyrmions, and magnetic vortices. Spintronics aims to make use of such tiny magnetic structures to store data or perform logic operations with very low power consumption, compared to today's dominant microelectronic components. However, the generation and stabilization of most of these magnetic textures is restricted to a few materials and achievable under very specific conditions (temperature, magnetic field…).
A new approach
An international collaboration led by HZB physicist Dr Sergio Valencia has now investigated a new approach that can be used to create and stabilize complex spin textures, such as radial vortices, in a variety of compounds. In a radial vortex, the magnetization points towards or away from the center of the structure. This type of magnetic configuration is usually highly unstable. Within this novel approach radial vortices are created with the help of superconducting structures while their stabilization is achieved by the presence of surface defects.
Superconducting YBCO-islands
Samples consist of micrometer size islands made of the high-temperature superconductor YBCO on which a ferromagnetic compound is deposited. On cooling the sample below 92 Kelvin (-181 °C), YBCO enters the superconducting state. In this state, an external magnetic field is applied and immediately removed. This process allows the penetration and pinning of magnetic flux quanta, which in turn creates a magnetic stray field. It is this stray field which produces new magnetic microstructures in the overlying ferromagnetic layer: spins emanate radially from the structure centre, as in a radial vortex.
The role of defects
As the temperature is increased, YBCO transits from the superconducting to a normal state. So the stray field created by YBCO islands disappears, and so should the magnetic radial vortex. However HZB researchers and collaborators have observed that the presence of surface defects prevents this to happen: the radial vortices partially retain the imprinted state, even when approaching room temperature.
"We use the magnetic field generated by the superconducting structures to imprint certain magnetic domains on the ferromagnets placed on them, and the surface defects to stabilize them. The magnetic structures are akin to that of a skyrmion and are interesting for spintronic applications,” explains Valencia.
Geometry matters
Smaller imprinted vortices were about 2 micrometres in diameter, about ten times the size of typical skyrmions. The team studied samples with circular and square geometries and found that circular geometries increased the stability of imprinted magnetic radial vortices.
"This is a novel way to create and stabilize such structures and it can be applied in a variety of ferromagnetic materials. These are good new prospects for the further development of superconducting spintronics," says Valencia.
- Nanosilver as an electrocatalyst for CO₂ reductionVia electrolysis, CO2 can be reduced to CO, a raw material for further chemical products such as fuels. Within the GreenQuest Project, an internation team led by HZB chemist Prashanth Menezes has now systematically investigated catalyst layers made of silver nanoparticles, varying both the size of the particles and their density. The best yield was achieved with nanoparticles with diameters of around 10 nm, which were loosely distributed. Furthermore, they demonstrated how the economic efficiency of the electrochemical cell can be enhanced by integrating an additional chemical reaction at the anode, enabling the simultaneous production of a valuable formic acid, hydrogen, and CO in one device.
- Spin waves inside a nano-oscillator imaged for the first timeFor the first time, researchers have directly imaged the magnetisation dynamics inside a spin Hall nano-oscillator — a nanoscale device that converts direct current into tunable microwave signals and is a promising building block for energy-efficient wireless communication and brain-inspired computing. A Swedish–German team led by the University of Gothenburg and Helmholtz-Zentrum Berlin (HZB) achieved this using time-resolved scanning transmission X-ray microscopy at the MAXYMUS instrument at BESSY II. The results, now published in Advanced Materials, reveal spin-wave features that had escaped previous, indirect measurement techniques.
- Joint power instead of duplicate structures:Berlin’s research community is further advancing its research excellence by establishing a high-performance, cross-institutional infrastructure for data and AI. With a joint agreement signed on 18 September 2026, the Berlin University Alliance (BUA), the Helmholtz-Zentrum Berlin (HZB) and the Zuse Institute Berlin (ZIB) are paving the way for a joint data science and AI centre in Berlin-Dahlem and Adlershof.