(M=Fe, Ni, Mn)

The family of layered antiferromagnetic insulators MPS₃, where M is a first row transition metal, have been previously found to undergo structural transitions under pressure which have been linked to a range of behaviours including metallisation and the emergence of superconductivity or new magnetic states[1-2]. The majority of published structural characterisations of these quasi-two-dimensional compounds rely on measurements of powder samples, whereas transport and magnetic properties are mostly derived from bulk single crystals.

We present a comparative study of the crystal structures of Fe, Ni and MnPS₃ under pressure from powder and single-crystal x-ray diffraction which highlight differences in behaviour between sample forms. Thanks to single crystal measurements, the collapse of the inter-planar separation which is linked to new magnetic and transport properties is characterised unambiguously for the first time, the identification of which is vital for any calculations of high-pressure properties in this family of materials. The contradiction of previous findings, and the nature of the impact of sample form with regards to current theoretically predicted high pressure structures[3] will also be discussed.

1. Wang, Y. et al., Nature Communications 9, 1 (2018).

2. Coak, M. J. et al., J. Phys.: Condens. Matter 32, 124003 (2019).

3. Evarestov, R. A. & Kuzmin, A., Journal of Computational Chemistry 41, 1337 (2020).