Emergence of a “devil’s staircase” in a spin-valve system
Hexagonal single crystal of SrCo6O11, with a sample diameter of approximately 0,2 millimetres.
The material exhibits distinct magnetization plateau connected with different spin configurations.
A Japanese-German team observes at BESSY II how spins form unusual magnetic structures in a complex cobalt oxide single crystal. Such a material offers new perspectives for spintronic applications.
While classical GMR systems are composed of metallic layers, complex oxides often intrinsically provide layered structures with alternating magnetic configurations that can act as spin valves. Cobalt oxides are a class of materials that can exhibit complex magnetic order that changes with increasing magnetic field, as for example indicated by distinct plateaux in the magnetization curve.
Magnetic structures mapped
A Japanese team of researchers led by the group of Associate Professor Hiroki Wadati at the University of Tokyo has been successful in characterizing the magnetic structures of the complex cobalt oxide SrCo6O11 using the high-field diffractometer of BESSY II. Synthesis of new materials often results in tiny samples, and the crystals studied here had a diameter of only 0.2 mm. With the very high sensitivity of resonant diffraction, a core competence at the UE46_PGM1 beamline of BESSY II, they managed to observe a fascinating type of spin order in the samples that are hardly visible by the bare eye. This order is called devil’s staircase, characterizing a phenomenon, where a pletora, in principle even an infinite number, of so-called commensurate superstructures - magnetic configurations in the present case - can be realized by tuning an external parameter, e.g., a magnetic field.
New options with a Devil's staircase
This exceeds the characteristic of a spin valve and may open new paths in spintronics. The research was carried out in close cooperation with German scientists from the Institut für Festkörper-und Werkstoffforschung Dresden and HZB. The results are now published in Physical Review Letters.
Reference: T. Matsuda, S. Partzsch, T. Tsuyama, E. Schierle, E. Weschke, J. Geck, T. Saito, S. Ishiwata, Y. Tokura, and H. Wadati, "Observation of a Devil’s Staircase in the Novel Spin-Valve System SrCo6O11", Physical Review Letters 114 (236403-1-5):
doi:10.1103/PhysRevLett.114.236403.
- Key technology for a future without fossil fuelsIn June and July 2025, catalyst researcher Nico Fischer spent some time at HZB. It was his sabbatical, he was relieved of his duties as Director of the Catalysis Institute in Cape Town for several months and was able to focus on research only. His institute is collaborating with HZB on two projects that aim to develop environmentally friendly alternatives using innovative catalyst technologies. The questions were asked by Antonia Rötger, HZB.
- 5000th patient treated with protons for eye tumoursFor more than 25 years, Charité – Universitätsmedizin Berlin and the Helmholtz-Zentrum Berlin (HZB) have been jointly offering proton radiation therapy for eye tumours. The HZB operates a proton accelerator in Berlin-Wannsee for this purpose, while Charité provides medical care for the patients. The 5000th patient was treated at the beginning of August.
- Iridium-free catalysts for acid water electrolysis investigatedHydrogen will play an important role, both as a fuel and as a raw material for industry. However, in order to produce relevant quantities of hydrogen, water electrolysis must become feasible on a multi-gigawatt scale. One bottleneck is the catalysts required, with iridium in particular being an extremely rare element. An international collaboration has therefore investigated iridium-free catalysts for acidic water electrolysis based on the element cobalt. Through investigations with various methods, among them experiments at the LiXEdrom at the BESSY II X-ray source in Berlin, they were able to elucidate processes that take place during water electrolysis in a cobalt-iron-lead oxide material as the anode. The study is published in Nature Energy.