(1. 内江师范学院 物理与电子信息工程学院，内江 641112；
2. Ames Laboratory, U.S. Department of Energy, Iowa State University, Ames, Iowa 50011-3020, USA)
摘 要: 本文在分析XRD谱、等温磁化曲线和等磁场变温磁化曲线的基础上，主要研究Ho3NiSi2合金的相结构、磁性相变和磁热性能。结果表明：采用不同方法制备的Ho3NiSi2合金中，第二相Ho5Si3含量存在明显差异，主相的原子占位也存在一定的差异。在低磁场下，Ho3NiSi2合金存在两个磁相变，一个是TSR=12 K的自旋重取向转变，另一个是居里温度为TC=39 K的铁磁-顺磁二级相变。在等温磁化过程中，存在磁场诱导的磁自旋重取向态向正常铁磁态转变的现象，因而在磁熵变(-ΔSM)-温度(T)图中，分别在TS和TC附近出现了两个同向的磁熵变峰，且在0~5 T磁场下，TSR和TC温度附近的最大磁熵变可分别达5.3 J/(kg·K)和12.7 J/(kg·K)。由于两种临界温度不同的磁相变会引起合金的制冷温跨增大，进而表现出大的相对制冷能力(RCP)；在0~5 T 磁场下，Ho3NiSi2合金的制冷温跨和相对制冷能力分别为57.2 K和375.5 J/kg。
关键字: Ho3NiSi2合金；磁相变；磁热效应
（1. College of Physics and Electronic Information Engineering, Neijiang Normal University, Neijiang 641100, China;
2. Ames Laboratory, U.S. Department of Energy, Iowa State University, Ames, Iowa 50011-2416, USA）
Abstract:In this paper, the phase, structure, magnetic transformation and magnetocaloric properties of Ho3NiSi2 alloy were studied based on XRD patterns, isothermal magnetization curves and constant magnetic field variable temperature magnetization curves. The results show that there are obvious differences in the content of the second phase Ho5Si3 and the atomic occupation of the main phase in the Ho3NiSi2 alloy prepared by different methods. There are two magnetic transitions in the Ho3NiSi2 alloy at low field. One is spin reorientation transition with TSR=12 K, and the other is ferromagnetic paramagnetic second-order transition with Curie temperature TC=39 K. In the isothermal magnetization process, there is a phenomenon of magnetic field induced magnetic spin reorientation ferromagnetic state transition to normal ferromagnetic state. Therefore, in the magnetic entropy change (-ΔSM)-temperature diagram, there are two peaks of magnetic entropy change in the same direction near TSR and TC, respectively. Under 0-5 T magnetic field, the maximum magnetic entropy change of Ho3NiSi2 alloy near TSR and TC can reach 5.3 J/(kg·K) and 12.7 J/(kg·K), respectively. Due to the contribution of two kinds of phase transformation magnetic entropy at different temperatures, the cooling temperature span of the alloy increases effectively, and then shows a great relative cooling capacity (RCP). The cooling temperature span and relative cooling capacity of Ho3NiSi2 alloy are 57.2 K and 375.5 J/kg, respectively.
Key words: Ho3NiSi2 alloy; magnetic transition; magnetocaloric properties
