采用铜模铸造法制备了 Mn1．15 Fe0．85 P0．55 Si0．45化合物,并对其物相结构、显微组织及磁热效应进行了研究.结果表明,化合物具有六角 Mn5．64 P3型主相和少量 Mn3 Fe2 Si3杂相；化合物的居里温度为305 K,热滞为13．5 K；在0~2 T 外磁场下的最大等温磁熵变为12．2 J/(kg·K),远远高于纯 Gd.同时为了探索大磁熵变的来源,采用 Landau 相变理论和“普适曲线”方法研究了该化合物的磁相变特性,Arrott 曲线分析表明,该化合物在居里温度附近发生了明显的一级相变,而“普适曲线”理论分析表明,该化合物的磁相变介于一级和二级之间.%Mn1 .1 5 Fe0.85 P0.5 5 Si0.45 ingots were prepared by arc melting and copper mould casting technique.The mi-crostructure and magnetocaloric effects were investigated by X-ray diffraction,scanning electron microscope and physical property measurement system.The results show that Mn1 .1 5 Fe0.85 P0.5 5 Si0.45 compound crystallizes into the hexagonal Mn5 .64 P3-type structure with small amount of Mn3 Fe2 Si3 impurity phases.The Curie temperature and thermal hysteresis are about 305 and 13.5 K respectively.The maximal magnetic entropy change of 12.2 J/(kg·K)in a field change of 2 T was obtained,which was much larger than that of pure Gd.To analyze the na-ture of the magnetic phase transition in detail,we have carried out the study of the critical behavior near the Cu-rie temperature for the compound by Landau theory and universal curves theory.The Arrott plots prove that the compound undergo a first-order magnetic transition,however universal curves theory indicate that the magnetic transition was between first-order and second-order.
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