稀土化合物中磁热效应与压热效应的关联机理与调控研究

This project will focus on the field of rare-earth compounds, and study on the magnetic properties, phase transition, magnetocaloric effect and barocaloric effect under the applied magnetic field and hydrostatic pressure. The new principles and reliable experimental methods will be developed in order to reveal the new way to improve the magnetocaloric and barocaloric performance of rare earth compounds. An effort will be made to study the new magnetic refrigeration cycle working in magnetic field and pressure. The latent heat measurement will be employed to study the large magnetocaloric effect of rare earth compounds, and the accuracy of latent heat measurement will be improved dramatically. Meantime, new home-made device will be developed which could accurately measure the latent heat under magnetic field. The results will be beneficial to reveal the mechanisms of large magnetocaloric effect. First principles electronic structure calculations will be performed in order to further study the magnetism, magneto-structural coupling effect, magnetocaloric effect and barocalorical effect in rare earth compounds. According to these results, the relationship between the microscopic electronic structure and macroscopic properties will be revealed, and coorelation between the large magnetocaloric effect and barocaloric effect in rare earth compounds will be clarified. These studies will be beneficial to pursue the magnetocaloric materials with a better performance.

本项目研究磁场和压力共同调控下稀土化合物的磁性、相变以及磁热效应和压热效应的变化规律，探索稀土化合物磁热效应、压热效应的实验原理，通过发展可靠的测量方法，揭示磁热效应和压热效应的相互关联机制，得到提高材料性能的新途径和新磁制冷工作原理。利用测量相变潜热的方法，研究稀土化合物在相变区域的大磁热效应，研究提高相变潜热测量精度的方法，实现在磁场、温度可控条件下精确测量相变潜热，进而揭示磁热效应的变化规律。同时，利用第一性原理电子结构计算来研究具有大磁热效应的稀土化合物的磁性、晶格等自由度的关联效应，建立微观电子结构与宏观物性之间的联系，阐明稀土化合物大磁热效应和压热效应的物理关联机制和调控方法，为材料性能设计提供依据。

材料磁热效应的变化规律是磁制冷技术的基础。材料不仅受磁场驱动，也受压力、原子空位的调控。本项目研究磁场压力以及原子空位调控下稀土化合物的磁性、相变以及磁热效应和压热效应的变化规律，探索稀土化合物磁热效应、压热效应的实验原理。发展可靠的测量方法并搭建了测量装置。揭示了多材料体系的物性、复杂相变下磁热效应和压热效应的相互关联机制。研究稀土化合物在相变区域的大磁热效应，研究提高磁热效应直接测量精度的方法，验证了材料磁热效应变化的规律性。利用第一性原理电子结构计算来研究具有大磁热效应的稀土化合物的磁性、晶格等自由度的关联效应，建立微观电子结构与宏观物性之间的联系，初步阐明稀土化合物大磁热效应和压热效应的物理关联机制和调控方法，为材料性能设计提供依据。研制了一台磁制冷样机，在0.9T磁场下，冷热端实现了23.8℃的大温差。