%0 Conference Paper
%A Eich, Andreas
%T CrAs at Low Temperatures and High Pressures, and the Development of Clamp Cells for Neutron Scattering Experiments at the MLZ
%M FZJ-2022-01839
%D 2022
%X Chromium Arsenide (CrAs) is the first reported Cr-based superconductor, exhibiting superconductivity above ~0.3 GPa with a maximum Tc ≈ 2.2 K at 1 GPa [1]. The superconducting phase region with a dome-like shape lies in the vicinity of a helically ordered antiferromagnetic state, with a region of coexistence of magnetism and superconductivity below ~0.7 GPa [2]. Short-range magnetic fluctuations are assumed to play an essential role for the pairing mechanism of the superconductivity, and CrAs is considered to be a model system for the interplay of superconductivity and helimagnetism [3].Up to now, most studies on CrAs were focused on magnetic and transport properties. The crystal structure of CrAs, however, has not been conclusively investigated yet, especially in dependence on the temperature. One aim of our investigation is thus to give an overview of the complete structural behavior of CrAs in dependence on temperature and on pressure. Our results based on synchrotron X-ray single-crystal diffraction reveal previously unknown features of CrAs related to the first-order phase transition from the paramagnetic to the antiferromagnetic state at TN ≈ 267 K: The isosymmetrical transition can induce a change in the microstructure, and one distinguished Cr–Cr distance exhibits anomalous behavior [4].In addition, we investigated the magnetic structure of CrAs at low temperature and high pressure by means of neutron single-crystal diffraction. The results show that the commonly accepted helical model is in fact not suited to describe the structure, although an unambiguous determination of the actually correct magnetic structure is not possible on the basis of our data.For a direct investigation of the crystal and magnetic structure of CrAs in and near the superconducting phase region, neutron scattering is the method of choice. To experimentally access the low temperature/high pressure region, we have developed two types of clamp cell suitable for use at the instruments DNS, POLI and MIRA at the Heinz Maier-Leibnitz Zentrum (MLZ) [5]. For each type, two variants were produced (CuBe and NiCrAl “Russian Alloy”), working up to 1.1 GPa and 1.5 GPa, respectively. First tests were performed to determine the load/pressure calibration curves (both with and without neutron radiation), to estimate its neutron absorption and background, and to measure magnetic reflections and the thermal response. Future tests will help to establish the cells at MLZ as a standard sample environment.
%B (Digital) Institute Seminar JCNS-2 (PhD Rehearsal Talk)
%C ,  (Germany + online event)
M2 , Germany + online event
%F PUB:(DE-HGF)31
%9 Talk (non-conference)
%U https://juser.fz-juelich.de/record/907108