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.

中文翻译：

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YCrO3 和 LaCrO3 中的自旋声子耦合和热力学行为：非弹性中子散射和晶格动力学

我们报告了磁性钙钛矿 YCrO3 和 LaCrO3 的详细的温度相关非弹性中子散射和从头算晶格动力学研究。来自 Cr 离子的磁中子散射随温度表现出显着变化，并且在低动量传递状态下占主导地位。包括磁相互作用在内的从头算计算表明，磁相互作用对低能和高能声子模式的影响非常显着。我们还表明，YCrO3 的非弹性中子谱模拟了 G 型反铁磁系统的磁振子谱，这与先前报道的化合物中的磁结构一致。压力相关的从头算晶格动力学计算用于计算正交晶系 YCrO3 中的各向异性热膨胀行为，这与顺磁相中的可用实验数据非常一致。我们发现涉及 Y 振动的低能量非谐声子模式对热膨胀行为的贡献最大。