MnCoGe基合金的磁性耦合、临界行为及其磁热效应调控研究

磁性耦合、临界行为及其磁热效应一直是室温磁制冷材料中具有挑战性的课题，人们发现原子替代对磁热材料具有重要影响并呈现出许多新奇而有趣的物理现象，然而其微观机理有待进一步澄清。本课题在前期对磁热材料的巨磁热效应和相变临界特性研究的基础上，选择巨磁热材料MnCoGe基合金体系为研究对象，通过对合金的晶体结构、离子替代、磁特性、磁热效应、磁性相变、临界行为等相关物理特性进行系统的研究和探索，将利用元素替代和掺杂的技术手段有选择地对该体系合金的结构、相变温度、磁热效应等物理特性进行有效的调控。给出原子占位和相变、临界行为、磁热效应的定量关系，通过对体系结构和相变的研究，结合运用Kouvel–Fisher方法等理论计算，重点给出结构相变、磁性相变、临界行为和随原子占位变化的机制，为深入理解结构-磁相变耦合的物理机制和研究合金巨磁热材料提供基础的实验和理论资料。

Magnetic coupling, critical behavior and magnetocaloric effect are difficult problems in room-temperature magnetic refrigeration materials. Although substituting partial atoms or introducing interstitial atoms has an important effect on magnetocaloric materials and some interesting results are obtained, the microscopic mechanism is still unclear. The crystal structure, ion substitution, magnetic properties, magnetocaloric properties, magnetic phase transition, critical behavior as well as the related physical properties of MnCoGe based alloys will be systematically studied in this proposal. Additional, we will use the elemental substitution/doping method to modify the crystal structure, transition temperature and magnetocaloric effect of MnCoGe alloys. The atom occupancy as well as its correlation with magnetostructural transformation, critical behavior and magnetocaloric effect will be investigated quantitatively by experimental and theoretical approachs, which mainly presents mechanism of magnetostructural transformation and critical behavior with atom occupancy. These results will be expected to provide some basic research data that are used to not only manifest the underlying physical mechanism of magnetostructural coupling, but also develop new investigation of giant magnetocaloric alloys.