Pressure-induced phase transition in the J1−J2 square lattice antiferromagnet RbMoOPO4Cl

Pressure-induced structural and magnetic ordering transitions in the J1–J2 square lattice antiferromagnets AMoOPO4Cl (A = K, Rb)

“…The optimization process under high pressure failed to sustain the atomic displacements and reverted back to the tetragonal phase, thereby eliminating the possibility. Experimentally, H. Takeda et al suggested that the high pressure phase of RbMoOPO 4 Cl above 2.6 GPa, indicated by anomalies in the pressure dependencies of the NMR shift and transferred hyperfine coupling constants, 8 might involve the mutual twisting of the MoO 5 Cl and PO 4 polyhedra, as occurred in MoOPO 4 , 7 breaking the mirror plane symmetry. However, the reliability of this hypothesis has yet to be validated through first principles calculations.…”

“…4(e), is ∼1.2 GPa, slightly smaller than the experimental value (∼2.6 GPa). 8 Since it does not account for kinetic effects in the calculations, hence, an underestimation of the actual value is plausible.…”

“…Given the assertion that magnetic interaction within the [MoPO 5 Cl] layer is highly sensitive to crystal variations, 6–8 it is reasonable to anticipate that a crystal phase transition from P 4/ nmm to P 4/ n should be accompanied by a magnetic configuration transition, as the magnetic coupling paths among Mo 5+ ions are substantially altered. Experimentally, the magnetic change from CAF ordering below 3.3 GPa to NAF one above 3.9 GPa has been detected by the NMR spectra.…”

“…Much attention has been paid to the square lattice magnets, where spins on the square lattice are entangled by the nearest neighbor (NN) interaction J 1 along the edges and the next nearest neighbor (NNN) interaction J 2 in the diagonal directions, not only for their dramatic variation of magnetic ground states such as the spin liquid/ice phase, spin chirality and spin nematic order, 1–5 owing to strong quantum fluctuations, but also for their exotic phase transitions sensitive to the external stimuli, such as pressure or chemical de-intercalation. 6–8 Theories on the Heisenberg model within a square lattice framework have predicted three magnetic collinear ordered ground states, 9 depending on the sign and relative magnitude of J 1 and J 2 , namely, the ferromagnetic (FM) phase (stabilized for with J 1 < 0), the Néel antiferromagnetic (NAF) phase ( with J 1 > 0) and the columnar antiferromagnetic (CAF) one (). It should be noted that, J > 0 indicates the antiferromagnetic interaction.…”

“…Actually, H. Takeda et al 8 performed magnetization and 31 P NMR measurements on RbMoOPO 4 Cl under high pressure up to 6.4 GPa. A pressure-induced structural phase transition takes place at 2.6 GPa, followed by a change of the magnetic configuration from CAF to NAF occurring over a finite range of pressure of 3.3–3.9 GPa, leaving a possibility for a quantum disorder phase in the intermediate pressure region.…”