Here we demonstrate that a ferromagnetic shape memory can be tuned conveniently by volume proportions within Heusler-type FeMnGa ( = 8, 6, 4, 2, and 0 at%) alloys over an extended temperature range. Preliminary X-ray diffraction experiments indicate that the FeMnGa alloys crystallize into a B cubic structure with space group for all compositions. Samples with compositions of = 0–4 at% show the co-existence of two cubic structures (B and L2). The temperature dependence of magnetization measurements on FeMnGa alloys under cooling-heating processes showed a moderate to an exceptionally large temperature hysteresis in a wider temperature range of 70–340 K, corresponding to the first-order diffusionless martensitic-to-austenite phase transformations. The curves obtained at various magnetic fields demonstrated that the magnitude and direction of temperature hysteresis is modified by volume proportions of Fe-Mn constituents. At 5, 150 and 300 K, hysteresis loop shows ferromagnetic (FM) behavior and the coercivity and remanence values vary with temperature and Mn content due to large exchange bias effects. Further ac magnetic susceptibility of FeMnGa measurements show a cusp with a maximum below 70 K corresponding to an antiferromagnetic (AFM) transition. Thermal shift of the AFM transition is attributed to the dominant AFM-FM interactions pertaining to the pinning efficiency at the interface between Fe and Mn. These findings provide a comprehensive understanding of AFM spin structure and ferromagnetic shape memory behavior in FeMnGa across cryogenic to 350 K temperatures.

中文翻译：

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通过 Heusler 型 Fe47-xMn24+xGa29 结构中的体积比例控制磁感应形状记忆行为

在这里，我们证明了铁磁形状记忆可以在扩展的温度范围内通过 Heusler 型 FeMnGa (= 8、6、4、2 和 0 at%) 合金的体积比例方便地调节。初步 X 射线衍射实验表明，FeMnGa 合金结晶成 B 立方结构，所有成分均具有空间群。成分 = 0–4 at% 的样品显示两种立方结构（B 和 L2）共存。 FeMnGa 合金在冷却-加热过程中磁化强度测量的温度依赖性显示出在 70-340 K 的更宽温度范围内中等至异常大的温度滞后，对应于一级无扩散马氏体到奥氏体相变。在不同磁场下获得的曲线表明，温度磁滞的大小和方向是通过 Fe-Mn 成分的体积比例来改变的。在 5、150 和 300 K 时，磁滞回线表现出铁磁 (FM) 行为，并且由于较大的交换偏置效应，矫顽力和剩磁值随温度和 Mn 含量而变化。 FeMnGa 的进一步交流磁化率测量结果表明，尖点的最大值低于 70 K，对应于反铁磁 (AFM) 转变。 AFM 转变的热位移归因于与 Fe 和 Mn 界面处的钉扎效率相关的主要 AFM-FM 相互作用。这些发现提供了对 FeMnGa 在低温至 350 K 温度范围内的 AFM 自旋结构和铁磁形状记忆行为的全面了解。