“VEKMAG” at BESSY II creates 3D magnetic fields in samples
A general view of the VEKMAG end-station. The vector magnet chamber (grey) is supported by a hexapod frame. Below the magnet one can distinguish the detector chamber (green) and in the forward direction the deposition chamber (dark grey) is displayed. The beam quality is monitored by a diagnostic chamber (yellow) positioned in front of the magnet chamber. © Dr. Tino Noll
Together with HZB, teams from the Universität Regensburg, from the Freie Universität Berlin and from the Ruhr Universität Bochum have jointly set up a unique measurement station at BESSY II: a vector electromagnet consisting of three mutually perpendicular Helmholtz coils which enables setting the local magnetic field at the sample position to any orientation desired. The first measurements of magnetic materials, spin systems, and nanostructured magnetic samples are scheduled for early 2015.
“We have been working on this project for almost six years”, reports HZB physicist Dr. Florin Radu. He is coordinating the project with the three universities. The deposition chamber for the samples was designed at Freie Universität Berlin. Ruhr Universität Bochum built the detector chambers, and Universität Regensburg developed the concepts for synchrotron beam-based ferromagnetic resonance experiments.
Rapid change of polarisation
In the meantime, Radu and his team ensured optimum characteristics of a new beamline for carrying out most sophisticated experiments: “We need an extremely stable beam, but we also want to be able to change the polarisation of the x-rays very rapidly”, he explains. “For that reason, we developed a hexapod vacuum chamber with six moveable legs supporting a mirror. By changing the leg positions slightly, we can change the orientation of the first mirror and thereby the polarisation of the x-ray beam in just seconds – about one hundred times faster than before.” The tests show that this prototype arrangement improves the signal-to-noise ratio by a factor of more than ten.
Temperature between 1,6 K and 500 K
The new experimental station will not only facilitate many different kinds of studies, particularly in the soft X-ray region, but will also permit to carry out completely new studies that require temperatures of 500 Kelvin right down to 1.6 Kelvin and magnetic fields as high as nine tesla. Simultaneously the X-rays can penetrate the individual atoms and excite their outer electrons, enabling magnetic properties of the individual elements to be distinguished.
The main assets of the new VEKMAG end-station are experimental specifications that are unique in comparison with stations operating at other international facilities. In particular for element-specific and time-resolved measurements of ferromagnetic and paramagnetic resonances, as well as for spectroscopic and scattering experiments VEKMAG offers a unique sample environment. However, “VEKMAG will only attain its full potential, once HZB has implemented a new innovative beam filling pattern with variable pulse lengths at full photon intensities”, according to Radu, because “we can then investigate rapid spin dynamics with sub-picosecond time resolutions.”
The VEKMAG project was funded by the German Federal Ministry for Education and Research (BMBF) through a grant of about four million Euros.
- Freeze casting - a guide to creating hierarchically structured materialsFreeze casting is an elegant, cost-effective manufacturing technique to produce highly porous materials with custom-designed hierarchical architectures, well-defined pore orientation, and multifunctional surface structures. Freeze-cast materials are suitable for many applications, from biomedicine to environmental engineering and energy technologies. An article in "Nature Reviews Methods Primer" now provides a guide to freeze-casting methods that includes an overview on current and future applications and highlights characterization techniques with a focus on X-ray tomoscopy.
- IRIS beamline at BESSY II extended with nanomicroscopyThe IRIS infrared beamline at the BESSY II storage ring now offers a fourth option for characterising materials, cells and even molecules on different length scales. The team has extended the IRIS beamline with an end station for nanospectroscopy and nanoimaging that enables spatial resolutions down to below 30 nanometres. The instrument is also available to external user groups.
- Clean cooking fuel with a great impact for southern AfricaBurning biomass for cooking causes harmful environmental and health issues. The German-South African GreenQUEST initiative is developing a clean household fuel. It aims to reduce climate-damaging CO2 emissions and to improve access to energy for households in sub-Saharan Africa.