Pressure-induced spin-state and phase transitions in the mono- LaCoO3 and multi-valent metastable La0.5Ba0.5CoO2.87 with one modified by pul

We suppose that accurate temperature dependent X-ray powder diffraction measurements in order to study unusual effect of crystal structure transformation of mono- LaCoO3 and multi-valent metastable La0.5Ba0.5CoO2.87 modified by pulsed magnetic field 20 Tesla. We expect to obtain reliable experimental data on the crystal structure, isotropic ADP for Co and O, as well as lattice parameters under applied pressure. Obtained X-ray diffraction results will be combined with pressure-dependent XMCD and neutron diffraction data as well as temperature-dependent XRD results at ID-22 and neutron diffraction (HRPT, PSI) in order to give us the opportunity to establish the correlations between crystal and magnetic structure changes and clarify the origin of magneto-structural phase transition near the PM→FM→AFM transitions, as well as to provide an input for a novel modeling methods based on the density functional theory (DFT, DFT+U, DFT+U+SO) and the dynamic mean-field theory (DFT+DMFT).

本研究拟开展精准的温度依赖X射线粉末衍射测试，以探究经20特斯拉脉冲磁场改性的单相LaCoO₃与多价亚稳态La₀.₅Ba₀.₅CoO₂.₈₇的晶体结构转变异常效应。我们期望获取可靠的实验数据，涵盖晶体结构、Co与O的各向同性原子位移参数（Atomic Displacement Parameters, ADP），以及外加压力条件下的晶格参数。所得X射线衍射结果将与基于ID-22线站的压力依赖X射线磁圆二色谱（X-ray Magnetic Circular Dichroism, XMCD）、中子衍射数据，以及在ID-22线站获得的温度依赖X射线衍射结果，以及保罗谢勒研究所（PSI）的高分辨粉末衍射仪（HRPT）测得的中子衍射数据相结合，从而得以明确晶体结构与磁结构变化之间的关联，阐明顺磁（PM）→铁磁（FM）→反铁磁（AFM）转变附近的磁-结构相变起源；同时为基于密度泛函理论（Density Functional Theory, DFT、DFT+U、DFT+U+SO）与动态平均场理论（Dynamic Mean-Field Theory, DFT+DMFT）的新型建模方法提供输入数据。