Large and sensitive magnetostriction (large strain induced by small magnetic fields) is highly desired for applications of magnetostrictive materials. However, it is difficult to simultaneously improve magnetostriction and reduce the switching field because magnetostriction and the switching field are both proportional to the magnetocrystalline anisotropy. To solve this fundamental challenge, we report that introducing tetragonal nanoprecipitates into a cubic matrix can facilitate large and sensitive magnetostriction even in random polycrystals. As exhibited in a proof-of-principle reference, Fe–Ga alloys, the figure of merit—defined by the saturation magnetostriction over the magnetocrystalline anisotropy constant—can be enhanced by over 5-fold through optimum aging of the solution-treated precursor. On the one hand, the aging-induced nanodispersive face-centered tetragonal (FCT) precipitates create local tetragonal distortion of the body-centered cubic (BCC) matrix, substantially enhancing the saturation magnetostriction to be comparable to that of single crystal materials. On the other hand, these precipitates randomly couple with the matrix at the nanoscale, resulting in the collapse of net magnetocrystalline anisotropy. Our findings not only provide a simple and feasible approach to enhance the magnetostriction performance of random polycrystalline ferromagnets but also provide important insights toward understanding the mechanism of heterogeneous magnetostriction.

对于磁致伸缩材料的应用，非常需要大而灵敏的磁致伸缩（由小磁场引起的大应变）。然而，由于磁致伸缩和开关场都与磁晶各向异性成比例，因此难以同时改善磁致伸缩和减小开关场。为了解决这一基本挑战，我们报告了将四方纳米沉淀物引入立方基质中，即使在随机多晶中也可以促进大而灵敏的磁致伸缩。如原理证明参考文献中所显示的，Fe-Ga合金的品质因数（通过饱和磁致伸缩对磁晶各向异性常数的定义）可以通过固溶处理前体的最佳时效提高5倍以上。一方面，老化诱导的纳米分散面心四方（FCT）沉淀物会形成体心立方（BCC）基质的局部四方畸变，从而大大提高了饱和磁致伸缩率，可与单晶材料媲美。另一方面，这些沉淀物在纳米级随机地与基体耦合，导致净磁晶各向异性的崩溃。我们的发现不仅为提高随机多晶铁磁体的磁致伸缩性能提供了一种简单可行的方法，而且为理解异质磁致伸缩机理提供了重要的见识。实质上增强了饱和磁致伸缩，使其可与单晶材料相比。另一方面，这些沉淀物在纳米级随机地与基体耦合，导致净磁晶各向异性的崩溃。我们的发现不仅为提高随机多晶铁磁体的磁致伸缩性能提供了一种简单可行的方法，而且为理解异质磁致伸缩机理提供了重要的见识。实质上增强了饱和磁致伸缩，使其可与单晶材料相比。另一方面，这些沉淀物在纳米级随机地与基体耦合，导致净磁晶各向异性的崩溃。我们的发现不仅为提高随机多晶铁磁体的磁致伸缩性能提供了一种简单可行的方法，而且为理解异质磁致伸缩机理提供了重要的见识。