This title appears in the Scientific Report : 2020 

Structural and macroscopic investigation of CrAs at low temperatures and high pressures
Eich, Andreas
Grzechnik, A. / Müller, Thomas / Paulmann, C. / Friese, K.
Streumethoden; JCNS-2
Streumethoden; PGI-4
Joint Polish-German Crystallographic Meeting 2020, Congress Center Wrocław University of Science and Technology (Poland), 2020-02-24 - 2020-02-27
Jülich Centre for Neutron Research (JCNS)
Materials and Processes for Energy and Transport Technologies
Quantum Condensed Matter: Magnetism, Superconductivity
Controlling Collective States
Controlling Collective States
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Chromium Arsenide (CrAs) is the first Cr-based superconductor, exhibiting pressure-induced superconductivity with a maximum Tc = 2.2 K at around 1 GPa [1,2] and the dome-like shaped superconducting phase region existing in the vicinity of a magnetically ordered state. The magnetic structure is described as double helices propagating along the c* direction with the spins in the (a,b) plane. The first-order phase transition from the helimagnetically ordered antiferromagnetic state to a paramagnetic state is clearly and consistently observed in our macroscopic measurements of magnetization, resistivity and heat capacity at TN ≈ 267 K. The transition is furthermore connected to an abrupt increase in unit cell volume of about 2.4%, though the symmetry of the crystal structure (Pnma, Z = 4) does presumably not change [3].As the understanding of the behaviour of the crystal structure of CrAs so far is based primarily on powder data, the objective of our work is to precisely determine the crystal structure by single crystal diffraction at low temperatures as well as at high pressures. This knowledge will serve as base for further studies of the crystal and magnetic structures of CrAs at simultaneously low temperatures and high pressures, in particular within or in the vicinity of the superconducting phase.For this, synchrotron x-ray diffraction experiments were performed on single crystals between 300 K and 20 K at ambient pressure, and between 0.92 GPa and 9.45 GPa at room temperature.The preliminary refinements show a good agreement with the literature data for the room temperature phase. Below the transition temperature the symmetry Pnma is preserved and the reflections can still be indexed with the orthorhombic cell, although a deterioration of the crystal quality is observed.[1] R.Y. Chen, N.L. Wang, Rep. Prog. Phys. 82, 012503 (2019)[2] W. Wu, et al., Nat. Commun. 5, 5508 (2014)[3] T. Suzuki, H. Ido, J. Appl. Phys. 69, 4624 (1991)