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.
- BESSY II: High-resolution insights into individual biomolecules and catalystsVery small biological samples and even individual biomolecules can now be examined under near-physiological conditions with high confidence at the BESSY II infrared beamline with a newly validated and improved technique: The nanoscale infrared spectroscopy (s-SNOM) with ultra-thin silicon-based membranes. An international team demonstrated after an initial proof of concept, that high-resolution (a few tens of nanometres) nano-IR measurements reliably match expected far-field IR spectra in an aqueous environment. This methodological advance provides a solid foundation for studying biomaterials or observing catalytic processes in a liquid environment.
- New method shows how molecular switches are influenced by their neighborsResearchers at Friedrich Schiller University Jena and the Helmholtz Centre Berlin (HZB) have, for the first time, been able to directly observe how the environment surrounding a molecular switch influences its electronic structure. Molecular switches are molecules that can be switched between two states by external influences such as changes in temperature—similar to a switch with the positions »On« and »Off«. Such molecules are being investigated as potential building blocks for future data storage devices or sensor materials. Using magnetic-field-dependent terahertz spectroscopy, the researchers have now, for the first time, been able to distinguish whether neighbouring molecules in a material are in the same or different states. The results have been published in the journal »Angewandte Chemie International Edition«.
- BESSY II is back in operation after maintenance shutdownOn 7 September 2026, BESSY II was set into operation after a four-week shutdown. BESSY II is scheduled to resume full user operation on 22 September.