论文标题
对称分辨的弹性异常在旋转的钴岩lacoo $ _3 $
Symmetry-resolved elastic anomalies in spin-crossover cobaltite LaCoO$_3$
论文作者
论文摘要
Ultrasound velocity measurements of the pseudo-cubic spin-crossover cobaltite LaCoO$_3$ and the lightly Ni-substituted La(Co$_{0.99}$Ni$_{0.01}$)O$_3$ reveal two types of symmetry-resolved elastic anomaly in the insulating paramagnetic state that are commonly observed in these compounds.散装模量的温度依赖性在冷却低于300 k至$ \ sim $ 70 k时表现出Curie型软化，表明存在轨道波动引起的同生晶格不稳定。四方和三角剪模量的温度依赖性在冷却低于300 K时表现出异常的硬化，表明出现弹性交叉引起的弹性交叉发生。本研究还表明，lacoo $ _3 $中的同一晶格不稳定性对NI替代敏感地抑制了，表明用光NI替换抑制了轨道波动。可以解释在Lacoo $ _3 $中的这种NI替代效应，以基于等值晶格的不稳定性，这是由于晶格与高速旋转状态和中间旋转状态之间波动的CO旋转状态的耦合所产生的。
Ultrasound velocity measurements of the pseudo-cubic spin-crossover cobaltite LaCoO$_3$ and the lightly Ni-substituted La(Co$_{0.99}$Ni$_{0.01}$)O$_3$ reveal two types of symmetry-resolved elastic anomaly in the insulating paramagnetic state that are commonly observed in these compounds. The temperature dependence of the bulk modulus exhibits Curie-type softening upon cooling below 300 K down to $\sim$70 K, indicating the presence of isostructural lattice instability arising from orbital fluctuations. The temperature dependence of the tetragonal and trigonal shear moduli exhibits unusual hardening upon cooling below 300 K, indicating the occurrence of elasticity crossover arising from the spin crossover. The present study also reveals that the isostructural lattice instability in LaCoO$_3$ is sensitively suppressed with the Ni substitution, indicating the suppression of orbital fluctuations with the light Ni substitution. This Ni substitution effect in LaCoO$_3$ can be explained on the basis that the isostructural lattice instability arises from the coupling of the lattice to the Co spin state fluctuating between the high-spin state and intermediate-spin state.
