Creating a Ferromagnetic Ground State with Tc Above Room Temperature in a Paramagnetic Alloy through Non-Equilibrium Nanostructuring,Advanced Materials

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Creating a Ferromagnetic Ground State with Tc Above Room Temperature in a Paramagnetic Alloy through Non-Equilibrium Nanostructuring
Advanced Materials ( IF 27.4 ) Pub Date : 2021-12-01 , DOI: 10.1002/adma.202108793
Xinglong Ye ₁ , Nuno Fortunato ₂ , Abhishek Sarkar _{1,

2} , Holger Geßwein ₃ , Di Wang _{1,

4} , Xiang Chen ₅ , Benedikt Eggert ₆ , Heiko Wende ₆ , Richard A Brand ₆ , Hongbin Zhang ₂ , Horst Hahn ₁ , Robert Kruk ₁

Affiliation

Materials with strong magnetostructural coupling have complex energy landscapes featuring multiple local ground states, thus making it possible to switch among distinct magnetic-electronic properties. However, these energy minima are rarely accessible by a mere application of an external stimuli to the system in equilibrium state. A ferromagnetic ground state, with T_c above room temperature, can be created in an initially paramagnetic alloy by nonequilibrium nanostructuring. By a dealloying process, bulk chemically disordered FeRh alloys are transformed into a nanoporous structure with the topology of a few nanometer-sized ligaments and nodes. Magnetometry and Mössbauer spectroscopy reveal the coexistence of two magnetic ground states, a conventional low-temperature spin-glass and a hitherto-unknown robust ferromagnetic phase. The emergence of the ferromagnetic phase is validated by density functional theory calculations showing that local tetragonal distortion induced by surface stress favors ferromagnetic ordering. The study provides a means for reaching conventionally inaccessible magnetic states, resulting in a complete on/off ferromagnetic–paramagnetic switching over a broad temperature range.

中文翻译：

通过非平衡纳米结构在顺磁合金中创建 Tc 高于室温的铁磁基态

具有强磁结构耦合的材料具有复杂的能量景观，具有多个局部基态，因此可以在不同的磁电子特性之间切换。然而，仅仅通过对处于平衡状态的系统施加外部刺激，很少能达到这些能量最小值。铁磁基态，T _c高于室温，可以通过非平衡纳米结构在初始顺磁性合金中产生。通过去合金化过程，大块化学无序的 FeRh 合金被转化为具有几个纳米级韧带和节点拓扑结构的纳米多孔结构。磁力测量和穆斯堡尔光谱揭示了两种磁性基态的共存，一种是传统的低温自旋玻璃，另一种是迄今为止未知的强铁磁相。铁磁相的出现通过密度泛函理论计算得到验证，表明由表面应力引起的局部四方畸变有利于铁磁有序。该研究提供了一种达到传统上难以接近的磁态的方法，从而在很宽的温度范围内实现完全的开/关铁磁-顺磁切换。

更新日期：2021-12-01

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