CEITEC BUT, Brno University of Technology, Purkyňova 123, 612 00Brno, Czech Republic.
Institute of Physical Engineering, Brno University of Technology, Technická 2, 616 69Brno, Czech Republic.
ACS Appl Mater Interfaces. 2023 Feb 15;15(6):8653-8665. doi: 10.1021/acsami.2c20107. Epub 2023 Jan 31.
Preparing and exploiting phase-change materials in the nanoscale form is an ongoing challenge for advanced material research. A common lasting obstacle is preserving the desired functionality present in the bulk form. Here, we present self-assembly routes of metamagnetic FeRh nanoislands with tunable sizes and shapes. While the phase transition between antiferromagnetic and ferromagnetic orders is largely suppressed in nanoislands formed on oxide substrates via thermodynamic nucleation, we find that nanomagnet arrays formed through solid-state dewetting keep their metamagnetic character. This behavior is strongly dependent on the resulting crystal faceting of the nanoislands, which is characteristic of each assembly route. Comparing the calculated surface energies for each magnetic phase of the nanoislands reveals that metamagnetism can be suppressed or allowed by specific geometrical configurations of the facets. Furthermore, we find that spatial confinement leads to very pronounced supercooling and the absence of phase separation in the nanoislands. Finally, the supported nanomagnets are chemically etched away from the substrates to inspect the phase transition properties of self-standing nanoparticles. We demonstrate that solid-state dewetting is a feasible and scalable way to obtain supported and free-standing FeRh nanomagnets with preserved metamagnetism.
在纳米尺度上制备和利用相变材料是先进材料研究中的一个持续挑战。一个常见的持久障碍是保持在块状形式中存在的所需功能。在这里，我们提出了具有可调尺寸和形状的亚铁磁 FeRh 纳米岛的自组装途径。虽然通过热力学成核在氧化物衬底上形成的纳米岛中很大程度上抑制了反铁磁和铁磁有序之间的相变，但我们发现通过固态去湿形成的纳米磁铁阵列保持其亚铁磁特性。这种行为强烈依赖于纳米岛的结晶面的结果，这是每种组装途径的特征。比较纳米岛每种磁性相的计算表面能表明，通过特定的面几何形状可以抑制或允许亚铁磁性。此外，我们发现空间限制导致非常明显的过冷和纳米岛中没有相分离。最后，将支撑的纳米磁铁从衬底上化学蚀刻以检查自支撑纳米粒子的相变特性。我们证明固态去湿是一种可行且可扩展的方法，可以获得具有保留亚铁磁特性的支撑和独立的 FeRh 纳米磁铁。
