Morley Sophie A, Porro Jose Maria, Hrabec Aleš, Rosamond Mark C, Venero Diego Alba, Linfield Edmund H, Burnell Gavin, Im Mi-Young, Fischer Peter, Langridge Sean, Marrows Christopher H
School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, United Kingdom.
Physics Department, University of California Santa Cruz, Santa Cruz, CA, 95064, USA.
Sci Rep. 2019 Nov 5;9(1):15989. doi: 10.1038/s41598-019-52460-7.
Designing and constructing model systems that embody the statistical mechanics of frustration is now possible using nanotechnology. We have arranged nanomagnets on a two-dimensional square lattice to form an artificial spin ice, and studied its fractional excitations, emergent magnetic monopoles, and how they respond to a driving field using X-ray magnetic microscopy. We observe a regime in which the monopole drift velocity is linear in field above a critical field for the onset of motion. The temperature dependence of the critical field can be described by introducing an interaction term into the Bean-Livingston model of field-assisted barrier hopping. By analogy with electrical charge drift motion, we define and measure a monopole mobility that is larger both for higher temperatures and stronger interactions between nanomagnets. The mobility in this linear regime is described by a creep model of zero-dimensional charges moving within a network of quasi-one-dimensional objects.
如今利用纳米技术设计并构建体现受挫统计力学的模型系统已成为可能。我们将纳米磁体排列在二维正方形晶格上，形成了一种人工自旋冰，并利用X射线磁显微镜研究了其分数激发、涌现的磁单极子，以及它们如何响应驱动场。我们观察到一个区域，在该区域中，高于运动起始的临界场时，单极子漂移速度与场强呈线性关系。通过在场辅助势垒跳跃的比恩 - 利文斯顿模型中引入一个相互作用项，可以描述临界场的温度依赖性。通过与电荷漂移运动类比，我们定义并测量了一种单极子迁移率，对于更高的温度以及纳米磁体之间更强的相互作用，这种迁移率都更大。在这个线性区域中的迁移率由零维电荷在准一维物体网络内移动的蠕变模型来描述。
