13. September 2018
Your story: Magnetic investigations at neutron and synchrotron sources
Sometimes we need a little bit of encouragement in order to make a big step: change scientific fields, publish a disruptive paper, learn something new. Maybe a DECTRIS sponsorship will do the trick? It did for Ankita Singh, a PhD student at the Indian Institute of Technology Roorkee, who wanted to extend her knowledge in neutron and synchrotron radiation.
“There is no better school to learn this than HERCULES”, explains Singh. Indeed, this one-month course on neutron and synchrotron radiation has been running since 1991, and has a long list of references among beamline scientists, physicists, chemists, even CEOs. Singh is a physicist, investigating properties of magnetic materials and their structures.
“Most materials are non-magnetic because the electrons occupying the same state have opposing spins, while the spins of the unpaired electrons are randomly oriented”, explains Singh, “however, in some materials magnetic moments of the unpaired electrons can align.” These magnetic materials are an interesting field of research, as their application extends from data storage to environmental containment. In order to tune the properties of a material for an application, its magnetic structure needs to be understood.
“Only two steps are required to determine a magnetic structure: solving its crystal structure and collecting neutron diffraction data”, smiles Singh. Due to their small magnetic moment, neutrons interact with the magnetic moment of the atom, which results in changes of the Bragg intensities. If the crystal structure is known, these intensity changes can be used to determine the axis along which the magnetic moments of particular atoms are aligned. Combining the axis with the crystal structure leads to the magnetic structure. Easy? Yes and no.
Singh researches materials whose magnetic properties vary with temperature, pressure and local structure. “Currently I am dealing with powders, but I plan to tackle other sample types. Also, I am interested in characterization of particular ions in the material”, comments Singh. “This is why I applied for HERCULES.”
HERCULES: experimental and theoretical sessions
At Saclay and ILL, she mastered neutron powder diffraction, and had her first experience with thin films and single crystals. “Although the leading role of neutrons for the studies of magnetic materials cannot be disputed, X-ray photons seem attractive”, adds Singh. While this could mostly be attributed to the possibility to probe small volumes using the highly collimated, intense, polarized and tunable synchrotron beam, the beamline availability is equally important. Magnetic investigations can nowadays be carried out at almost every synchrotron source, using magnetic X-ray scattering, X-ray spectroscopy or a combination of these techniques. At Soleil and ESRF, Singh was introduced to X-ray absorption and emission spectroscopy, two techniques necessary to resolve the oxidation and spin states of ions in the investigated material.
“HERCULES has the right balance of theoretical and experimental knowledge. The school definitely gave new momentum to my research. Thank you for the sponsorship”, concludes Ankita.
This year’s HERCULES School has finished. Those interested in the course will be happy to know that the next call for applications will open in fall 2018, so start working on your applications. At DECTRIS, we will also be busy. No, development of a single neutron counting detector is not really our thing. But, X-ray absorption and emission spectroscopy, magnetic X-ray scattering and X-ray topography on all kind of samples sound really great! We will be looking for young researchers and their science to feature on our website.
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