稀土-过渡族氧化物中大磁热效应物理机制的研究

In hydrogen gas liquefaction area, space technology and low temperature field of science platform building technology, large magnetocaloric effect material at low temperature have important potential, therefore, the physical mechanism research for large magnetocaloric effect at low temperature area is particularly significance. In previous work, we found that rare earth-transition oxides with half full electronic occupancy (Gd3+, Eu2+) have giant magnetocaloric effect, but the inner physical mechanism is not clear. Applicants found that the large magnetocaloric effect is related to the half full occupped 4f electronic state. We found the maximum magnetic entropy change value for GdFeO3 polycrystalline is 50.2 J/kg K for the first time, which preliminary verify the guess. To further in-depth study, the project will choose the pure and doped GdFeO3 polycrystalline and single crystal as the research object, combined with the first principles calculation, establishing the intrinsic relationship between the micro electronic structure, finding out the physical mechanism for the giant magnetocaloric effect resulted from the half full occupped 4f electronic state. This application helps to strengthen the understanding of the basic problem of magnetism, at the same time to take new insight into searching and designing magnetic refrigerating agent with large magnetic entropy change in low temperature area.

低温区大磁热效应材料在氢气的液化、空间技术及低温与极低温科学平台的搭建等等领域具有重要的潜力，因此，研究低温区中大磁热效应的物理机制显得尤为重要。在前期的工作中我们发现稀土-过渡族氧化物中稀土位半满电子填充（Gd3+，Eu2+）时存在较同族化合物更大的磁热效应，但其中大磁熵变的物理图象并不清晰。申请人认为其中大的磁热效应与其中半满填充的4f电子相关。我们最近在实验中发现GdFeO3 中的磁熵变值高达50.2 J/kg K，初步验证了猜想。为了进一步深入研究，本项目选取GdFeO3 掺杂样品体系多晶及单晶为实验研究主体，结合第一性原理计算分析，建立起微观电子结构与体系宏观磁有序和磁热效应的本质联系，研究4f电子半满填充状态导致大磁熵变的物理机制。本项申请有助于加强对基本磁学问题的理解，同时为寻找和设计具有大磁熵变的低温区磁制冷工质提供新的思路。

低温区大磁热效应材料在氢气的液化、空间技术及低温与极低温科学平台的搭建等等领域具有重要的潜力。稀土-过渡族氧化物中稀土位半满电子填（Gd3+，Eu2+）时存在较同族化合物更大的磁热效应，但其中大磁熵变的物理图象并不清晰。本项目中，成功制备并研究了GdFeO3掺杂样品体系多晶及单晶，GdScO3单晶与GdCoO3外延薄膜的磁性与磁热效应，发现其大的磁热效应与其中半满填充的4f电子具有直接关系。本项申请有助于加强对基本磁学问题的理解，同时为寻找和设计具有大磁熵变的低温区磁制冷工质提供新的思路。在本项目的资助下，目前已经发表SCI论文6篇（还有2篇SCI论文正在撰写中），协助培养了硕士研究生3名。达到了基金申请书预期的目标。