中文摘要：

利用机械合金化（MA）结合放电等离子烧结（SPS）技术, 制备了Mn1.2Fe0.8P0.76Ge0.24磁制冷材料,并采用SEM观察烧结样品的显微组织, 利用中子衍射、超导量子干涉磁强计（SQUID）、差示扫描量热仪（DSC）和X射线衍射（XRD）等手段对相变过程和磁热性能进行了研究.结果表明： 烧结样品显微组织均匀致密, Mn1.2Fe0.8P0.76Ge0.24化合物具有六方Fe2P型晶体结构.外加磁场和温度的变化都可以引起材料的磁热相变, 即顺磁相与铁磁相之间的可逆一级相变.材料的磁熵变与相转变的程度有密切关系, 随着外加磁场的增大或温度的降低,合金由顺磁相向铁磁相转变, 从而使材料磁熵变增大. 分析发现,材料的磁熵变大小与相转变过程中发生转变的相变百分比是直接对应的,温度诱导相变与磁场诱导相变所得结果一致.

英文摘要：

In recent years, the MnFePGe compound has drawn tremendous attention not only for its excellent magnetocaloric effect （MCE）, but also for its great commercial interest.Compared with other advanced MCE materials such as GdSiGe, MnFePAs, etc.,it possesses many practical advantages such as more abundant raw materials,lower fabrication costs as well as better environmental amity. In this work, Mn1.2Fe0.8P0.76Ge0.24 compound was prepared by mechanical milling and subsequent spark plasma sintering （SPS） technique, its microstructure was investigated by SEM, meanwhile the relationship between phase transition and the properties was investigated by neutrondiffraction, SQUID, DSC and XRD. The results show that the Mn1.2Fe0.8P0.76Ge0.24 compound is compact, and possess a hexagonal Fe2P-type crystal structure. Generally, either applied magnetic field or temperature change will induce the transformation between paramagnetic phase and ferromagnetic phase. When the applied magnetic field increased or temperature reduced, paramagnetic phase transformed to ferromagnetic phase and caused the magnetic entropy change to become larger. It is found that the magnetic entropy change of Mn1.2Fe0.8P0.76Ge0.24 compound is directly corresponding to the percentage of the phase transition.