Magnetic-field-induced first-order magnetostructural transition (MFI-FOMST) brings about an ample variety of intriguing magnetoresponsive effects including magnetocaloric effect, magnetoresistance and magnetostrain. Metamagnetic shape memory alloys (MSMAs) exhibit MFI-FOMST and thus giant magnetoresponsive effects, but the critical field for complete and reversible MFI-FOMST, (μ₀∆H)_min, is too high (usually >5 T), which has been a longstanding bottleneck for practical applications. Here, we successfully achieved complete and reversible MFI-FOMST under a low field of 1.5 T, which can be generated by permanent magnets, in a prototype MSMA. The significant reduction of (μ₀∆H)_min is realized by simultaneously enlarging the distance between Curie transition and magnetostructural transition and manipulating the geometric compatibility between the transforming phases. The low (μ₀∆H)_min provides a great opportunity for attaining low-field-induced large reversible magnetoresponsive effects. For instance, a large reversible magnetocaloric effect is achieved under 1.5 T. Our realization of low-field-induced complete and reversible first-order magnetostructural transition may push a significant step forward towards the practical use of MSMAs. This work is instructive for developing novel magnetic materials with low-field-actuated first-order phase transition for applications as magnetic actuators, magnetoresistors and solid-state refrigerants.

磁场诱导的一阶磁结构转变 (MFI-FOMST) 带来了大量有趣的磁响应效应，包括磁热效应、磁阻效应和磁应变效应。变磁形状记忆合金 (MSMA) 表现出 MFI-FOMST，因此具有巨磁响应效应，但完整和可逆 MFI-FOMST 的临界场 ( μ ₀ ∆ H ) _min太高（通常 >5 T），这一直长期存在的实际应用瓶颈。在这里，我们在原型 MSMA 中成功地在 1.5 T 的低场下实现了完整且可逆的 MFI-FOMST，这可以由永磁体产生。( μ ₀ ∆ H )的显着减少_min是通过同时扩大居里跃迁和磁结构跃迁之间的距离并操纵相变相之间的几何相容性来实现的。低 ( μ ₀ ∆ H )_分钟为获得低场诱导的大可逆磁响应效应提供了一个很好的机会。例如，在 1.5 T 下实现了大的可逆磁热效应。我们实现低场诱导的完整和可逆的一阶磁结构转变可能推动 MSMA 的实际应用向前迈出重要一步。这项工作对于开发具有低场驱动的一阶相变的新型磁性材料具有指导意义，可用于磁致动器、磁阻器和固态制冷剂等应用。