铜模铸造法制备Mn_(1.15)Fe_(0.85)P_(0.55)Si_(0.45)化合物及其磁相变研究

Investigation on magnetic phase transition for Mn_(1. 15)Fe_(0. 85)P_(0. 55)Si_(0. 45) compound prepared by copper mould casting

采用铜模铸造法制备了Mn1.15Fe0.85P0.55Si0.45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Mn5.64P3型主相和少量Mn3Fe2Si3 杂相;化合物的居里温度为305K,热滞为13.5K;在0~2T外磁场下的最大等温磁熵变为12.2J/（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.

Abstruct: Mn1. 15Fe0. 85P0. 55Si0. 45 ingots were prepared by arc melting and copper mould casting technique. The microstructure and magnetocaloric effects were investigated by X-ray diffraction,scanning electron microscope and physical property measurement system. The results show that Mn1. 15Fe0. 85P0. 55Si0. 45 compound crystallizes into the hexagonal Mn5. 64P3-type structure with small amount of Mn3Fe2Si3 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 of2 T was obtained,which was much larger than that of pure Gd. To analyze the nature of the magnetic phase transition in detail,we have carried out the study of the critical behavior near the Curie 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.