Berlin 2018 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 16: Magnetic characterization techniques

MA 16.7: Vortrag

Dienstag, 13. März 2018, 11:15–11:30, H 0112

Neutron Depolarization Microscope for Imaging of Ferromagnetic Phase Transitions: Ni₃Al and HgCr₂Se₄ under pressure — •Pau Jorba¹, Michael Schulz², Daniel Hussey³, Boris Khaykovich⁴, Muhuammad Abir⁴, Marc Seifert¹, Vladimir Tsurkan⁵, Allois Loidl⁵, and Christian Pfleiderer¹ — ¹Physik-Department, Technische Universität München, Germany — ²Heinz-Maier-Leibnitz Zentrum (MLZ), TUM, Germany — ³NIST, Gaithersburg, MD, USA — ⁴Nuclear Reactor Laboratory, Massachusetts Institute of Technology, USA — ⁵Center for Electronic Correlations and Magnetism, University of Augsburg, Germany

We performed neutron depolarization imaging of a large Ni₃Al crystal, and a small HgCr₂Se₄ spinel under pressure, to probe bulk magnetic inhomogeneities in the ferromagnetic transition temperature with the spatial resolution about 100 µm. To obtain these spatially resolved depolarization images we employed a neutron microscope equipped with Wolter optic, a neutron image-forming lens, as well as a focusing neutron guide. The depolarization images on Ni₃Al clearly show that the sample doesn’t homogeneously go through the ferromagnetic transition. The results on the chromium spinel highlight the advantage of this technique especially for small samples, or sample environments with restricted sample space, as we are able to significantly improve the resolution while decreasing the acquisition time. The novel optical design that enabled acquisition of the high spatial resolution neutron depolarization images is described in detail and image results are compared to a conventional radiography setup without a lens.