Beschreibung
The single-crystal diffractometer HEiDi at MLZ has been designed for a wide range of scientific applications, offering a broad spectrum of thermal and hot neutrons, excellent resolution, access to a large region of reciprocal space, low absorption and high sensitivity for light elements. This makes HEiDi a versatile tool for extended studies on many structures for nowadays topics in physics, chemistry and mineralogy, e.g. investigations of a wide variety of magnetic compounds, components for batteries as well as geomaterials and small molecular structures. In addition to atomic positions, details like mean square displacements or (partial/local) disorder and incommensurability and twinning are also thoroughly analyzed.
The sample environment of HEiDi plays a key role for these studies: our options for temperature-dependent measurements have been continuously optimized to perform low-temperature measurements down to ~2 K, e.g. on magnetic structures in the case of a recently finished DFG project on orthoferrites (SA 3688/1-1) [Cha17]. Also, a mirror furnace has been developed allowing not only measurements of the position and mobility of ions like lithium or oxygen in potential battery materials up to 1300 K but also enabling studies on excess oxygen incorporation in brownmillerites as part of another DFG project (ME 3488/2-1), generating a better understanding of the underlying diffusion processes and structural changes [Mag21].
The recent optimisation of HEiDi for tiny samples << 1 mm³ was accompanied by introducing high-pressure cells within two BMBF projects (05K16PA3, 05K19PA2), establishing isotropic high-pressure experiments on single crystals up to 10 GPa as new application on HEiDi [Grz20]. Aside from new diamond anvil cells and clamp cells, the later project contained the development of a prototype of an Li-glass based area detector (PSD, in collaboration with JCNS) optimized for short wavelengths in order to enable more efficient detection of reciprocal space and weak signals.
Concerning HEiDi’s future, we intend to build a larger version of the PSD prototype in order to further increase its efficiency and range of possibilities. To combine its short wavelengths with a large PSD enables us to support the growing scientific demand for total scattering studies, namely by offering PDF analysis (pair distribution function) to study locally disordered materials (including those for technological advances) as new application on HEiDi.
[Cha17] T. Chatterji et al. (2017); AIP Advances , 045106
[Mag21] F. Magro et al.(2021); J. Appl. Cryst. 54, 822-829.
[Grz20] A. Grzechnik et al (2020); J. Appl. Cryst. 53(1), 1-6 2020.
