中文摘要：

研究了Mn1.28Fe0.67P1-xSix（x=0.52,0.54,0.56,0.58）系列化合物的结构、磁性和磁热效应.研究结果表明：该系列化合物都形成了Fe2P型六角结构,空间群为P-62m;随着Si含量的增加化合物的晶格常数a和晶胞体积V都增大;化合物经历了由铁磁到顺磁的一级相变过程;化合物的热滞呈现有规律的变化（2.5～6.1K）,当Si含量为0.56时,化合物的热滞最小（2.5K）,居里温度从232K（x=0.52）升高到302K（x=0.58）;化合物具有良好的室温磁热效应,在1.5T外磁场下,最大磁熵变由x=0.58时的6J/（kg.K）增大到x=0.52时的10J/（kg.K）.

英文摘要：

In this paper we investigated the structural,magnetic and magnetocaloric properties of Mn1.28Fe0.67P1-xSix（x=0.52,0.54,0.56,0.58） compounds.The results show that the samples crystallize in the Fe2P-type hexagonal structure with space group of P-62 m.The lattice parameter a and unit cell volume increase orderly with increasing the content of Si.All compounds experience a ferromagnetic-paramagnetic first-order phase transition.The thermal hysteresis of the compounds fluctuates between 2.5K to 6.1K and the minimal thermal hysteresis of about 2.5K is found in Mn1.28Fe0.67P0.44Si0.56 compound.The Curie temperature gradually increases from 232K（x=0.52） to 302K（x=0.58） with increasing the Si content.The maximal magnetic-entropy change increases from 6J/（kg·K）（x= 0.58） to 10J/（kg·K） for a magnetic field change of 1.5T.