Abstract Ni-Mn-based metamagnetic shape memory alloys have been extensively studied due to their multifunctional properties including magnetocaloric effect (MCE), magnetoresistance effect, and magnetic-field-induced strain. However, the large intrinsic thermal hysteresis of these alloys sets a limit on further development for practical applications. Here, with a few atomic percent Al substitution, we greatly reduced the thermal hysteresis and transformation temperature interval while maintaining the large magnetization difference (ΔM) between austenite and martensite. The simultaneous achievement of a large ΔM and low thermal hysteresis leads to a remarkable enhancement in MCE upon Al substitution, and a maximum magnetic entropy change of 31.6 J/kg K is achieved under a field of 5 T in Ni39Co11Mn40Sn8Al2. Furthermore, our in situ high-energy X-ray diffraction experiments show that the Ni39Co11Mn40Sn8Al2 has good geometric compatibility between austenite and martensite, which accounts for the reduced thermal hysteresis in this alloy. This study is instructive for the development of high-performance magnetocaloric materials in the metamagnetic shape memory alloys.

中文翻译：

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Al置换对Ni-Co-Mn-Sn多功能合金磁热性能的影响

摘要 Ni-Mn 基变磁形状记忆合金由于其多功能特性，包括磁热效应（MCE）、磁阻效应和磁场诱导应变而被广泛研究。然而，这些合金较大的固有热滞后限制了实际应用的进一步发展。在这里，通过少量原子百分比的 Al 替代，我们大大降低了热滞后和转变温度区间，同时保持了奥氏体和马氏体之间的大磁化差异 (ΔM)。同时实现大 ΔM 和低热滞后导致 Al 替代后 MCE 显着增强，并且在 Ni39Co11Mn40Sn8Al2 中在 5 T 场下实现了 31.6 J/kg K 的最大磁熵变。此外，我们的原位高能 X 射线衍射实验表明 Ni39Co11Mn40Sn8Al2 在奥氏体和马氏体之间具有良好的几何相容性，这是该合金热滞后降低的原因。该研究对开发用于超磁形状记忆合金的高性能磁热材料具有指导意义。