Lab News & Scientific Highlights
A new twist on a mesmerising story
The Einstein–de Haas effect, first demonstrated more than a century ago, provides an intriguing link between magnetism and rotation in ferromagnetic materials. An international team led by ETH physicist Steven Johnson now established that the effect has also a central role in ultrafast processes that happen at the sub-picosecond timescale — and thus deliver fresh insight into materials that might form the basis for novel devices.
Photoswitching in a Molecular Cube
Niéli’s paper is accepted in the Journal of Physical Chemistry Letters! We use X-ray absorption spectroscopy and X-ray magnetic circular dichroism to watch directly how the Co and Fe ions in a molecular cube change their oxidation states and turn from diamagnetic into paramagnetic units upon light irradiation.
A new spin in nano-electronics
In recent years, electronic data processing has been evolving in one direction only: The industry has downsized its components to the nanometer range. But this process is now reaching its physical limits. Researchers at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and the Paul Scherrer Institut (PSI) are therefore exploring spin waves or so-called magnons – a promising alternative for transporting information in more compact microchips. Cooperating with international partners, they have successfully generated and controlled extremely short-wavelength spin waves. The physicists achieved this feat by harnessing a natural magnetic phenomenon, as they explain in the journal Nature Nanotechnology.
Additive Manufacturing of High Entropy Alloys
Additive manufacturing of high-entropy alloys combines the mechanical properties of this novel family of alloys with the geometrical freedom and complexity required by modern designs. An approach to additive manufacturing of high-entropy alloys has been developed based on 3D extrusion of inks containing a blend of oxide nanopowders (Co3O4 + Cr2O3 + Fe2O3 + NiO), followed by co-reduction to metals, inter-diffusion and sintering to near-full density CoCrFeNi in H2. A complex phase evolution path is observed by in-situ X-ray diffraction in extruded filaments: the oxide phases undergo reduction and the resulting metals inter-diffuse, ultimately forming the desired fcc-CoCrFeNi alloy (see figure). Linked to this phase evolution is a complex micro-structural one, from loosely packed oxide particles to fully-annealed, metallic CoCrFeNi with 99.6 ± 0.1% relative density. CoCrFeNi micro-lattices are created with strut diameters as low as 100 μm and excellent mechanical properties at ambient and cryogenic temperatures.
New Method for Calculating Soft X-ray Magnetic Circular Dichroism Spectra
Scientists have demonstrated in a combined theoretical and experimental effort that the new ligand-field density functional theory method (LF-DFT) can be used to calculate the X-ray absorption spectra (XAS) and X-ray magnetic circular dichroism (XMCD) of lanthanide compounds from purely structural input.
Watching electrons and switching bits on
Electronics should get smaller, faster, and above all more energy-efficient. These themes are also present in several research groups at PSI. From incremental improvements to complete rethinking – who is currently working on what?
Revealing the role of microstructure architecture on strength and ductility of Ni microwires by in-situ synchrotron X-ray diffraction
The effect of diameter reduction on the mechanical properties of cold-drawn nickel microwires has been analyzed by a combination of in situ X-ray diffraction and electron backscatter diffraction observations.
Sub-ns magnetic domain wall motion dynamics
Magnetic domain walls can be reliably displaced by electrical currents, allowing for the fabrication of retentive magnetic memory elements without mechanically moving parts, such as e.g. the magnetic racetrack memory. Researchers in a joint collaboration between the PolLux endstation of the Swiss Light Source and the University of Leeds were able to investigate the dynamics of magnetic domain wall motion with a sub-ns time step, providing a substantial step forward towards the unraveling of the physical processes behind the current- and magnetic field-induced motion of magnetic domains.
A High Resolution Digital Image Correlation Study under Multiaxial Loading
We have developed a new cruciform geometry with reduced thickness at the center, which allows reaching high plastic strain under equibiaxial loading. The novel thinning method results in excellent surface quality, suitable for electron backscatter diffraction (EBSD) and high-resolution digital image correlation (HRDIC) investigations. We performed an in-situ HRDIC study on a 304 austenitic stainless steel using the new cruciform geometry to follow the slip activity under uniaxial and equibiaxial loadings.