We study the stabilisation of clusters and lattices of cuboidal particles with long-ranged magnetic dipolar and short-ranged surface interactions. Two realistic systems were considered: one with magnetisation oriented in the [001] crystallographic direction and the other with magnetisation along the [111] direction. We have studied magnetic nanocube clusters first in the limit of T = 0 K intending to elucidate the structural genesis of low energy configurations and then analysed finite-temperature behaviour of the same systems in simulations. Our results demonstrate that dipolar coupling can stabilise nanoparticle assemblies with cubic, planar, and linear arrangements seen previously in experiments. While attractive surface energy supports the formation of super-cubes, repulsion results in the elongated structures in the form of rods and chains. We observe the stabilisation of the ferromagnetic planar arrangements of the cubes standing on their corners and in contact over edges. We illustrate that minimal energy structures depend only on the size of the assembly and balance of surface repulsion and magnetic dipolar coupling. The presented results are scalable to different particle sizes and material parameters.

中文翻译：

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由表面和磁性相互作用指导的纳米立方体超结构的组装。

我们研究具有长距离磁偶极和短距离表面相互作用的长方体粒子的簇和晶格的稳定性。考虑了两个现实的系统：一个磁化方向为[001]结晶方向，另一个磁化方向为[111]方向。我们在T的极限中首先研究了磁性纳米立方体团簇= 0 K旨在阐明低能量配置的结构成因，然后在仿真中分析同一系统的有限温度行为。我们的结果表明，偶极耦合可以稳定具有先前在实验中看到的立方，平面和线性排列的纳米粒子组件。吸引人的表面能支持超级立方体的形成，而排斥则导致杆和链形式的细长结构。我们观察到立足于其角并接触边缘的立方体的铁磁平面布置的稳定。我们说明最小的能量结构仅取决于组件的大小以及表面斥力和磁偶极耦合的平衡。呈现的结果可扩展至不同的粒径和材料参数。