Lab News & Scientific Highlights

Figure caption: Sketch of the 3D Fermi surface of d-AlNiCo (left) and its experimental cross-sections in the indicated planes (right) showing vanishing pseudogap in the quasiperiodic directions.

Fermi states and anisotropy of Brillouin zone scattering in the decagonal Al–Ni–Co quasicrystal

Quasicrystals (QCs) are intermetallic alloys where excellent long-range order coexists with lack of translational symmetry in one or more dimensions. These materials have a high potential in application as a material for a solar cells, hydrogen storage applications, heat insulating layers, and others.

3D image of the buckyball structure investigated. In the right picture the distribution of Cobalt is shown in orange. (The solid line corresponds to 1 micrometre or 1 thousandth of a millimetre).

Element-Specific X-Ray Phase Tomography of 3D Structures at the Nanoscale

Recent advances in fabrication techniques to create mesoscopic 3D structures have led to significant developments in a variety of fields including biology, photonics, and magnetism. Further progress in these areas benefits from their full quantitative and structural characterization.

Schematic diagram of vortex core reversal process. The vortex core magnetisation reverses its orientation when crossing a domain boundary (black down arrow to white up arrow).

Nanoscale switch for vortex polarization mediated by Bloch core formation in magnetic hybrid systems

Vortices are fundamental magnetic topological structures characterized by a curling magnetization around a highly stable nanometric core.

Figure: Left top, one of the XRPD measured patterns and the corresponding fit. Left bottom, the fitted size distribution (green bars) with the maghemite (shell) and magnetite (core) weight fractions as a function of diameter. Right, the corresponding saturation magnetization as a function of shell relative thickness for samples with the same average diameter. Inset, a sketch of a core-shell nanoparticle as modeled.

Correlating the Core-Shell Composition and the Surface Structure to the Magnetic Properties for Magnetite-Maghemite Nanoparticles in the 5-15 nm Range

Very small superparamagnetic iron oxide nanoparticles were characterized by innovative synchrotron X-ray total scattering methods and Debye function analysis, developed at the X04SA Materials Science beamline of SLS.

View of a Mn19 molecule on the gold surface. The surface-induced changes of the oxidation state and magnetic properties of the constituent Mn ions have been probed by X-ray absorption spectroscopy and X-ray magnetic circular dichroism.

Reduction of Mn19 Coordination Clusters on a Gold Surface

The surface-induced changes of the oxidation state and magnetic properties of Mn ion clusters have been probed by X-ray absorption spectroscopy and X-ray magnetic circular dichroism.

Schematics of the iMott spin detector attached to an ARPES analyzer.

Concept of a multichannel spin-resolving electron analyzer based on Mott scattering

The spin of electron plays a crucial role in many physical phenomena, ranging from the obvious example of magnetism, via novel materials for spintronics applications, to high-temperature superconductivity. Spin- and angle-resolved photoelectron spectroscopy (SARPES) gives the most direct access to the spin aspects of the electronic structure, but the one-channel detection principle of all presently available SARPES spectrometers severely limits their efficiency. A team of Swiss and Russian scientists has developed a revolutionary concept of a multichannel electron spin detector based on Mott scattering as the spin selective process and imaging-type electron optics.

(a) Rhombohedral distortion of the pseudocubic La1−xSrxMnO3 lattice; (b) GGA+U theoretical FS; (c,d) Experimental FS cross-sections, with the shadow contours manifesting the lattice distortion.

Fermi Surface of Three-Dimensional La1−xSrxMnO3 Explored by Soft-X-Ray ARPES: Rhombohedral Lattice Distortion and its Effect on Magnetoresistance

A research team led by scientists from the Swiss Light Source has for the first time established three-dimensional (3D) electronic structure of the perovskite compound La1−xSrxMnO3 connected with its colossal magnetoresistance. Instrumental for this study has been the use of the new experimental technique of soft-x-ray ARPES, available at the ADRESS beamline, with its intrinsically sharp definition of 3D electron momentum.

Left: Structure of BaFe2As2 with the motion pattern of the A1g phonon mode (red arrows). 
Right: Pump-induced change of diffraction intensity of the (1 0 5) reflection

Ultrafast structural dynamics of the Fe-pnictide parent compound BaFe2As2

Understanding the interplay of the various degrees of freedom such as the electrons, spins and lattice is essential for many complex materials, including the high-temperature superconductors.

Magnetization dynamics inside a 5 µm x 5 µm structure.(a) Time-resolved PEEM images using XMCD as a magnetic contrast mechanism recorded at a given time delay t after the laser pulse and (b) extracted XMCD contrast as a function of the time delay t for three different ROI, defined in the inset image by the coloured area superimposed on the non-dichroic X-ray absorption of the structure. The 0° incoming laser direction with respect to the structure edge is indicated in the inset by the laser in-plane wave v…

Nanoscale sub-100 picosecond all-optical magnetization switching in GdFeCo microstructure

Ultrafast magnetization reversal driven by femtosecond laser pulses has been shown to be a promising way to write information. Seeking to improve the recording density has raised intriguing fundamental questions about the feasibility of combining ultrafast temporal resolution with sub-wavelength spatial resolution for magnetic recording. Here we report on the experimental demonstration of nanoscale sub-100 ps all-optical magnetization switching, providing a path to sub-wavelength magnetic recording.