Designer 3D Magnetic Mesostructures

在最近一篇引人注目的论文中，肖等人。Argonne National实验室的研究表明，可以通过从铅盐溶液到石墨衬底的电沉积来生长“结构可调”的铅中观结构(样品的尺寸介于微观“原子”尺度和宏观“整体”尺度之间，在这些尺度上，特定的几何形状不再影响物理性质)。只需改变电极电位，就可以实现各种不同的样品形态，从规则的多面体和纳米线到多足和雪花。这些结构是真正的三维(3D)超导介晶，几乎没有体缺陷和完美光滑的小平面，其磁性由其尺寸和形状决定。同样的沉积方法应该很容易推广到许多铁磁性金属和合金。现在首次有可能可控地制备规则的小平面3D介晶，而不存在光刻图案化薄膜结构所特有的无序和粗糙表面/边缘。重要的是，这些三维细观结构的尺寸与铁磁性和超导中发现的相关特征长度和尺度(例如铁磁区尺寸和/或磁区壁宽度或超导相干长度和/或磁场穿透深度)相比较，而不是被广泛研究的纳米粒子/团簇和纳米线。随着这些3D结构的大小和形状的变化，不同过程之间的竞争应该会导致丰富的新物理现象，具有很强的开发潜力。在与Argonne小组的合作中，我们已经证明了表面/形状效应可以完全控制这些材料的磁化，从而为‘设计’具有理想的、可开发的特性的晶体打开了可能性。我们建议在巴斯大学电化学和纳米物理方面的成熟小组与南安普敦和安特卫普的理论家之间的合作下，极大地扩大这项工作的范围。我们计划生长和研究各种形貌的超导和铁磁介晶，以及铁磁-超导体混合核壳结构和连续杂化网络。最有希望生产的材料将使用霍尔纳米磁测量和/或磁阻测量来系统地表征。实验结果将通过与定制的最先进的3D微磁模拟和/或3D Ginzburg-Landau方程的解进行比较来解释。还将确定和探索开发这些新型磁性材料的机会。

In a remarkable recent paper Xiao et al. at Argonne National Laboratories demonstrated that 'architecture-tuneable' Pb mesostructures (samples whose dimensions lie between microscopic 'atomic' scales and macroscopic 'bulk' scales at which the specific geometry no longer plays a role for physical properties) can be grown by electrodeposition from lead salt solutions onto graphite substrates. Simply varying the electrode potentials allows an extraordinary variety of different sample morphologies to be realised, ranging from regular polyhedra and nanowires to multipods and 'snowflakes'. These structures are truly three-dimensional (3D) superconducting mesocrystals with few bulk defects and perfectly smooth faceted faces, whose magnetic properties are dominated by their size and shape. The same deposition method should be readily extendable to many ferromagnetic metals and alloys. For the first time it is now possible to controllably fabricate regular faceted 3D mesoscrystals without the disorder and rough surfaces/edges characteristic of lithographically-patterned thin film structures. Crucially, the dimensions of these 3D mesostructures are comparable with the relevant characteristic lengthscales found in ferromagnetism and superconductivity (e.g. ferromagnetic domain size and/or domain wall width or superconducting coherence length and/or magnetic field penetration depth) in contrast to widely studied nanoscale particles/clusters and nanowires. Competition between different processes as a function of the size and shape of these 3D structures should lead to rich new physical phenomena with strong potential for exploitation. In collaboration with the Argonne group we have shown that surface/shape effects can completely dominate the magnetisation of these materials, opening up the possibility of 'designing' crystals with desirable, exploitable properties. We propose to considerably extend the scope of this work within a collaboration between well established groups in electrochemistry and nanoscale physics at the University of Bath and theoreticians in Southampton and Antwerp. We plan to grow and investigate both superconducting and ferromagnetic mesocrystals with a wide range of morphologies, as well as hybrid ferromagnetic-superconductor core-shell structures and continuous hybrid networks. The most promising materials produced will be systematically characterised using Hall nanomagnetometry and/or magnetoresistance measurements. Experimental results will be interpreted by comparison with tailor-made state-of-the-art 3D micromagnetic simulations and/or solutions of the 3D Ginzburg-Landau equation. Opportunities for exploitation of these novel magnetic materials will also be identified and explored.