(1. 內(nèi)江師范學(xué)院 物理與電子信息工程學(xué)院，內(nèi)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譜、等溫磁化曲線和等磁場(chǎng)變溫磁化曲線的基礎(chǔ)上，主要研究Ho3NiSi2合金的相結(jié)構(gòu)、磁性相變和磁熱性能。結(jié)果表明：采用不同方法制備的Ho3NiSi2合金中，第二相Ho5Si3含量存在明顯差異，主相的原子占位也存在一定的差異。在低磁場(chǎng)下，Ho3NiSi2合金存在兩個(gè)磁相變，一個(gè)是TSR=12 K的自旋重取向轉(zhuǎn)變，另一個(gè)是居里溫度為T(mén)C=39 K的鐵磁-順磁二級(jí)相變。在等溫磁化過(guò)程中，存在磁場(chǎng)誘導(dǎo)的磁自旋重取向態(tài)向正常鐵磁態(tài)轉(zhuǎn)變的現(xiàn)象，因而在磁熵變(-ΔSM)-溫度(T)圖中，分別在TS和TC附近出現(xiàn)了兩個(gè)同向的磁熵變峰，且在0~5 T磁場(chǎng)下，TSR和TC溫度附近的最大磁熵變可分別達(dá)5.3 J/(kg·K)和12.7 J/(kg·K)。由于兩種臨界溫度不同的磁相變會(huì)引起合金的制冷溫跨增大，進(jìn)而表現(xiàn)出大的相對(duì)制冷能力(RCP)；在0~5 T 磁場(chǎng)下，Ho3NiSi2合金的制冷溫跨和相對(duì)制冷能力分別為57.2 K和375.5 J/kg。
關(guān)鍵字: Ho3NiSi2合金；磁相變；磁熱效應(yīng)
（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
