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 dTN/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

Effects of magnetic anisotropy and exchange in TmFe17

Neutron diffraction experiments have been carried out to study the magnetocrystalline anisotropy of two 2b and 2d Tm sublattices and four 4f, 6g, 12j, and 12k Fe sublattices in ferrimagnetic compound Tm2Fe17 space group P63 mmc . We have determined the temperature dependence of the magnitude and orientation of magnetization for each of the thulium and iron sublattices in the range 10 300 K. A spontaneous rotation at about 90 K of the Tm and Fe sublattice magnetizations from the c axis to the basal plane is accompanied by a drastic change in the magnetization magnitude, signifying a large magnetization anisotropy. Both Tm sublattices exhibit an easy axis type of the magnetocrystalline anisotropy. The Fe sublattices manifest both the uniaxial and planar anisotropy types. The sublattice formed by Fe atoms at the 4f position reveals the largest planar anisotropy constant. The Fe atoms at the 12j position show a uniaxial anisotropy. We find that the inelastic neutron scattering spectra measured below and above the spin reorientation transition are remarkably differen