High-pressure effects on structural, magnetic, and vibrational properties of van der Waals antiferromagnet MnPS3

The crystal structure, vibrational spectra, and magnetic structure of quasi-two-dimensional layered van der Waals material MnPS₃ were studied using x-ray diffraction and Raman spectroscopy at high pressures up to 28 GPa, and neutron diffraction up to 3.6 GPa, respectively. A structural phase transition between two monoclinic modifications of the same C2/m symmetry was observed, evolving gradually in the pressure range of about 1–6 GPa. The transition is accompanied by abrupt shortening of lattice parameters, significant reduction of the monoclinic distortion, and anomalies in the pressure behavior of several Raman-mode frequencies. No more structural phase transitions were revealed in the studied pressure range. The antiferromagnetic (AFM) state with a propagation vector k= (0, 0, 0) remains stable in ambient pressure and high-pressure structural phases of MnPS₃ at least up to 3.6 GPa. The Néel temperature increases noticeably with a pressure coefficient of dT_N/dP=6.7 K/GPa, leading to modification of the dominant first-neighbor magnetic interaction exchange parameter with a relevant coefficient dJ₁/dP≈−0.6 meV/GPa. This observation is in contrast to the pressure behavior of FePS₃, demonstrating modification of the AFM state from 2D-like to 3D-like at the similar pressure-induced structural phase transition. The different pressure response of the magnetic states of
MnPS₃ and FePS₃ is analyzed in terms of competing in-plane and interplane magnetic interactions.