柔性薄膜LaCoO3中应力和氧空位对铁磁绝缘性作用机理研究

应力作用和氧空位是LaCoO3薄膜形成铁磁绝缘性的两个关键因素，虽然目前已有许多工作被报道，但国际上对该薄膜铁磁绝缘性的形成机制仍缺乏深入理解。由于机制不明，不仅限制了薄膜的广泛应用，也使得研发性质更优的钙钛矿铁磁绝缘体面临较大的材料设计难题。本申请项目拟利用柔性衬底取代传统的刚性衬底制备LaCoO3单晶薄膜，研究应力效应和氧空位对铁磁绝缘性的作用机制。在核共振背散射谱、X射线吸收精细结构谱、电子自旋共振谱对氧空位的含量、Co离子的电子结构、自旋态的测量基础之上，并结合宏观磁电性质的测试，就能利用柔性衬底易于弯曲的特点，实现在氧空位作用不变的情况下，探索不同类型的应力对薄膜磁性的调控规律。同时又可实现在应力作用不变的情况下，探索氧空位对薄膜磁性的调控规律。最后通过密度泛函计算和物理模型的建立，全面揭示出LaCoO3薄膜形成铁磁绝缘性的物理机制。

Strain effect and oxygen vacancies play a key role for the ferromagnetic insulation of LaCoO3 thin film. Although some related studies have been reported, the intrinsic mechanism of the formation of ferromagnetic insulation has not been completely clarified. This issue not only limits the wide application of LaCoO3 thin films, but also makes it difficult to design other perovskite ferromagnetic insulators with better properties. In this project, we plan to fabricate LaCoO3 thin films with the fexible substrate rather than the conventional rigid substrates, which will be in favor of finding the origin of the ferromagnetic insulation in LaCoO3 thin film. Based on the measurements of nuclear resonance back scattering spectrometry, X-ray absorption fine structure spectrometry, electronic spin resonance spectrometry，we can obtain some important information about LaCoO3 thin films, including the contents of oxygen vacancies, the electronic structure of Co ions, and the spin ordering state of Co ions. Together with the understanding of macroscopic magnetic-electronic properties detected by physical property measurement system, we are able to study the strain how to solely effect on ferromagnetism in LaCoO3 thin film as the effect of oxygen vacancies remains unchanged due to a high flexibility of the present substrates. Moreover, we can also study the oxygen vacancies solely effect on the ferromagnetism as the strain remains unchanged. Finally, we can disclose the physical mechanism of the formation of ferromagnetic insulation in LaCoO3 thin film thoroughly with the help of density functional calculation and the establishment of physical model.