Abstract Four polycrystaline Fe2P-type Ho6(Fe,Mn)Bi2 intermetallic compounds (space group P 6 ‾ 2 m , No. 189, hP9) have been studied using magnetic techniques in order to explore their ability as magnetocaloric materials, and study the critical behavior of the paramagnetic (PM) to ferromagnetic (FM) transitions to obtain a deeper understanding of the range of the magnetic interactions. The obtained critical exponents β, γ and δ for the four compounds studied (Ho6MnBi2, Ho6FeBi2, Ho6(Mn0.5Fe0.5)Bi2, Ho6(Mn0.75Fe0.25)Bi2) point to long-range order interactions, as they are close to those of the Mean Field Universality class. All of the compounds show relevant magnetocaloric properties over a very broad temperature range, limited by the PM-FM transition and a spin-reorientation one, well separated in all cases. They present very high values of the refrigerant capacities (from 520 J/kg to 709 J/kg at 5 T), good magnetic entropy changes (from 3.4 to 5.7 J/(kgK) at 5 T), and a flat and wide temperature span for the working temperature range (nearly 200 K for Ho6MnBi2, 80 K for Ho6FeBi2 at 5T). The change in properties with composition proves that the magnetocaloric properties can be tuned in Fe2P-type compounds to accommodate different refrigeration applications. Finally, the magnetocaloric scaling laws have been successfully tested and universal curves for the magnetic entropy change have also been obtained in the PM-FM transition region.

中文翻译：

---

Ho6(Fe,Mn)Bi2金属间化合物的磁热特性、磁相互作用和临界行为

摘要 利用磁性技术研究了四种多晶 Fe2P 型 Ho6(Fe,Mn)Bi2 金属间化合物（空间群 P 6 ‾ 2 m , No. 189, hP9），以探索它们作为磁热材料的能力，并研究其临界顺磁 (PM) 到铁磁 (FM) 跃迁的行为，以获得对磁相互作用范围的更深入了解。所研究的四种化合物（Ho6MnBi2、Ho6FeBi2、Ho6(Mn0.5Fe0.5)Bi2、Ho6(Mn0.75Fe0.25)Bi2）的临界指数β、γ和δ指向长程有序相互作用，因为它们是接近平均场普遍性类的那些。所有化合物在很宽的温度范围内都显示出相关的磁热特性，受 PM-FM 转变和自旋重定向的限制，在所有情况下都很好地分离。它们具有非常高的制冷剂容量值（5 T 时从 520 J/kg 到 709 J/kg）、良好的磁熵变（5 T 时从 3.4 到 5.7 J/(kgK)）以及平坦宽广的温度工作温度范围的跨度（Ho6MnBi2 接近 200 K，5T 时 Ho6FeBi2 接近 80 K）。特性随成分的变化证明可以在 Fe2P 型化合物中调整磁热特性以适应不同的制冷应用。最后，成功地测试了磁热标度定律，并在 PM-FM 过渡区获得了磁熵变的通用曲线。对于 5T 的 Ho6FeBi2 为 80 K）。特性随成分的变化证明可以在 Fe2P 型化合物中调整磁热特性以适应不同的制冷应用。最后，成功地测试了磁热标度定律，并在 PM-FM 过渡区获得了磁熵变的通用曲线。对于 5T 的 Ho6FeBi2 为 80 K）。特性随成分的变化证明可以在 Fe2P 型化合物中调整磁热特性以适应不同的制冷应用。最后，成功地测试了磁热标度定律，并在 PM-FM 过渡区获得了磁熵变的通用曲线。