强磁场下层状钙钛矿结构Fe4+基氧化物的制备和物性研究

Although Fe4+ and Mn3+ has the same electronic configuration 3d4, and Fe4+ and Mn3+ -based oxides both belong to strongly correlated electronic systems, they exhibit different physical properties. To understand this difference, especially the nature of the charge disproportionation effect in Fe4+ -based oxides, we select Sr3Fe2O7 with Ruddlesden-Popper structure as the object of study. By doping 4d and 5d elements with more spatially extended oribitals at Fe site, we intend to recognized the evolution of electronic structure and quantum phase transiton upon the variation in U/W covering 3d to 4d and 5d oxides, and further enhance the understanding of the d electron states. We aim at establishing the correlation between magnetic field, microstructure, and the electronic and magnetic properties and elucidate the influence and mechanism of high magnetic field on the quantum phase transition and the multiple quantum order such as the spin, charge, and orbital, through the prepation of materials and the study of properties under high magnetic field. Moreover, we may explore and discover new physical phenomena and effects in Sr3Fe2O7 and the doped samples under high magnetic field. We may also reveal the origin of charge disproportionation and shed light on the nature of antiferromagnetic transtion in Sr3Fe2O7.

Fe4+与Mn3+具有相同的电子构型3d4，而且Fe4+基氧化物和Mn3+基氧化物都属于强关联电子体系，但是它们却表现出迥然不同的物理性质。为了理解这一差异，尤其是Fe4+基氧化物中所出现的电荷歧化效应的本质，本项目拟选取Ruddlesden-Popper结构Fe4+基氧化物Sr3Fe2O7为研究对象，通过Fe位掺杂替代轨道半径更加拓展的4d和5d元素，认识从3d到4d和5d氧化物，随着电子关联强度U/W的变化而导致的体系电子结构和量子相变行为的演变规律，进一步增强对d电子态的理解；通过强磁场下材料制备和强磁场下物性研究，建立磁场—微结构—电磁性质变化的关联，阐明强磁场对体系的自旋、电荷、轨道等多重量子序及量子相变的影响规律和作用机制，探索和发现强磁场下Sr3Fe2O7及其掺杂体系中可能存在的新物理现象和效应，进而揭示Sr3Fe2O7中电荷歧化的起因及Sr3Fe2O7中反铁磁转变的本质。

（1）具有相同3d4电子构型的Fe4+基氧化物和Mn3+基氧化物都属于强关联电子体系，但物性迥异，本项目的研究目标就是通过为了对Sr3Fe2O7中电子关联强度U/W的变化而导致的体系电子结构和量子相变行为的演变规律，进一步增强对d电子态的理解。.（2）通过Fe位掺杂3d及轨道半径更加拓展的4d和5d元素，研究从3d到4d和5d氧化物，随着电子关联强度U/W的变化而导致的体系电子结构和量子相变行为的演变规律，进一步增强对d电子态的理解。.（3）强磁场条件下钙钛矿结构Cr基和Fe/Cr基氧化物的磁性、磁卡效应、磁电效应研究揭示其中蕴含丰富物性与效应。