Spin–phonon coupling and thermodynamic behaviour in YCrO₃ and LaCrO₃: inelastic neutron scattering and lattice dynamics

Abstract

We report detailed temperature-dependent inelastic neutron scattering and ab initio lattice dynamics investigation of magnetic perovskites YCrO3 and LaCrO3. The magnetic neutron scattering from the Cr ions exhibits significant changes with temperature and dominates at low momentum transfer regime. Ab initio calculations performed including magnetic interactions show that the effect of magnetic interactions is very significant on the low- as well as high-energy phonon modes. We have also shown that the inelastic neutron spectrum of YCrO3 mimics the magnon spectrum from a G-type antiferromagnetic system, which is consistent with previously reported magnetic structure in the compound. The pressure-dependent ab initio lattice dynamics calculations are used to calculate the anisotropic thermal expansion behaviour in orthorhombic YCrO3, which is in excellent agreement with the available experimental data in the paramagnetic phase. We identify that the low energy anharmonic phonon modes involving Y vibrations contribute maximum to the thermal expansion behaviour.

Sodium diffusion and dynamics in Na2Ti3O7: neutron scattering and ab initio simulations

“…The data analysis was carried out using the Mantid 50,51 software in the incoherent one-phonon approximation. This is a reasonable approximation 57 since the Q-range of the INS data comprises several Brillouin zones. The INS measured scattering function S(Q, E) is related [58][59][60] to the neutron-weighted phonon density of states g (n) (E) as follows:…”

“…The data analysis was carried out using Mantid 50,51 software in the incoherent one-phonon approximation. This is a reasonable approximation 57 since the Q -range of the INS data comprises several Brillouin zones. The INS measured scattering function S ( Q , E ) is related 58–60 to the neutron-weighted phonon density of states g ( n ) ( E ) as follows:where the + or − signs correspond to the energy loss or gain of the neutrons, respectively; n ( E , T ) = [exp( E / k B T ) − 1] −1 , T is temperature, k B is the Boltzmann's constant, and A is a normalization constant.…”

“…The temperature dependence of the phonon density of states in Na 2 Ti 3 O 7 was measured 57 using the MARI time of flight direct geometry spectrometer at ISIS, UK. The polycrystalline sample of Na 2 Ti 3 O 7 was kept in a glass tube of about 10 mm inner diameter.…”

A comprehensive review on the ferroelectric orthochromates: Synthesis, property, and application

“…11(c)) [76]. As listed in Table 2, some other magnetic anomalies were suggested at ∼ 10 and 230 K. These need to be carefully checked with modern neutron scattering technique that is powerful and unique for solving magnetic structures and determining spin excitations and fluctuations [149,163,305,306].…”

Insights into the structural symmetry of single-crystal YCrO$_3$ from synchrotron X-ray diffraction

“…There exist many unsolved problems and reported controversies, for example, the disharmony between reported centrosymmetric structural model and appearance of ferroelectricity [5,6,7,8,9,10]. As a consequence, to date, there is still subject of numerous experimental and theoretical studies [3,4,9,10,11,12,13,14,15,16,17,18].…”