Band Jahn–Teller type structural instabilities of cubic Mn2YZ Heusler compounds causing tetragonal distortions can be predicted by ab initio band‐structure calculations. This allows for identification of new Heusler materials with tunable magnetic and structural properties that can satisfy the demands for spintronic applications, such as in spin‐transfer torque‐based devices.

We report a new H x CrS 2 -based crystalline/amorphous layered material synthesized by soft chemical methods. We study the structural nature and composition of this material with atomic resolution scanning transmission electron microscopy (STEM), revealing a complex structure consisting of alternating layers of amorphous and crystalline lamellae. Furthermore, the magnetic properties show evidence for increased magnetic frustration compared to the parent compound NaCrS 2 . Finally, we show that this material can be exfoliated, thus providing a facile synthesis method for chromium-sulfide-based ultrathin layers. The material reported herein can not only be a source of new thin TMD-related sheets for potential application in catalysis but also be of interest for realizing new 2D magnetic materials.

The chromium arsenides BaCr2As2 and BaCrFeAs2 with ThCr2Si2 type structure (space group I4/mmm; also adopted by '122' iron arsenide superconductors) have been suggested as mother compounds for possible new superconductors. DFT-based calculations of the electronic structure evidence metallic antiferromagnetic ground states for both compounds. By powder neutron diffraction we confirm for BaCr2As2 a robust ordering in the antiferromagnetic G-type structure at TN = 580 K with µCr = 1.9 µB at T = 2 K. Anomalies in the lattice parameters point to magneto-structural coupling effects. In BaCrFeAs2 the Cr and Fe atoms randomly occupy the transition-metal site and G-type order is found below 265 K with µ Cr/Fe = 1.1 µB.57 Fe Mössbauer spectroscopy demonstrates that only a small ordered moment is associated with the Fe atoms, in agreement with electronic structure calculations with µFe ∼ 0. The temperature dependence of the hyperfine field does not follow that of the total moments. Both compounds are metallic but show large enhancements of the linear specific heat coefficient γ with respect to the band structure values. The metallic state and the electrical transport in BaCrFeAs2 is dominated by the atomic disorder of Cr and Fe and partial magnetic disorder of Fe. Our results indicate that Néel-type order is unfavorable for the Fe moments and thus it is destabilized with increasing iron content.

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The structural and electronic properties of BaCr 2 As 2 , which is isostructural to the 122 iron arsenide superconductors, are studied at high pressures using synchrotron x-ray powder diffraction, electrical resistivity measurements, and first-principles calculations. At a pressure of about 18.5 GPa, an isostructural phase transition to a collapsed tetragonal phase is observed, similar to that in BaFe 2 As 2 . In both phases, BaCr 2 As 2 is a normal metal. Electronic structure calculations suggest a metallic and antiferromagnetic ground state with G-type magnetic order for the collapsed tetragonal phase.