Colloquium: Artificial spin ice: Designing and imaging magnetic frustration
Colloquium: Artificial spin ice: Designing and imaging magnetic frustration
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DOI：
10.1103/revmodphys.85.1473
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发表时间：
2013-10-02
影响因子：
44.1
通讯作者：
Schiffer, Peter
中科院分区：
文献类型：
--
作者：
Nisoli, Cristiano;Moessner, Roderich;Schiffer, Peter
挫折，竞争相互作用的存在，在物理科学中无处不在，是退化和无序的根源，这反过来又会产生新的和有趣的物理现象。也许没有什么地方比相关自旋系统更简单，在那里它已经被研究得最详细。在无序磁性材料中，挫折导致spingglass现象，类似于结构玻璃和神经网络的行为。在结构有序的磁性材料中，它也是过去二十年来广泛的理论和实验研究的主题。这样的几何挫折打开了一扇窗户，看到了一系列全新的奇异行为。这包括自旋液体，其中自旋继续波动到最低温度，以及自旋冰，即使在进入拓扑库仑相的低温极限下，它似乎也保留了宏观熵。在过去的七年里，通过创造人工受挫磁系统，在研究受挫方面开辟了一个新的视角。这些材料由光刻制造的单畴铁磁纳米结构阵列组成，其行为类似于巨大的伊辛自旋。纳米结构的相互作用可以通过适当选择它们的几何性质和在（受抑）晶格上的排列来控制。材料的自由度不仅可以直接调节，而且可以单独观察。实验研究已经发现了无序系统和非热“颗粒”材料的非平衡物理学的有趣联系，同时揭示了自旋冰材料及其分数磁激发的强烈类比，使企业具有明显的跨学科风味。实验结果也与理论和计算分析密切相关，并与经典的受抑磁性模型联系起来，这些模型迄今未被观察到的方面在这里找到了实验实现。相当大的实验和理论进展，在这一领域进行了审查，包括连接到其他挫折的现象，并在这个迅速扩大的领域的进展前景进行了概述。
Frustration, the presence of competing interactions, is ubiquitous in the physical sciences and is a source of degeneracy and disorder, which in turn gives rise to new and interesting physical phenomena. Perhaps nowhere does it occur more simply than in correlated spin systems, where it has been studied in the most detail. In disordered magnetic materials, frustration leads to spinglass phenomena, with analogies to the behavior of structural glasses and neural networks. In structurally ordered magnetic materials, it has also been the topic of extensive theoretical and experimental studies over the past two decades. Such geometrical frustration has opened a window to a wide range of fundamentally new exotic behavior. This includes spin liquids in which the spins continue to fluctuate down to the lowest temperatures, and spin ice, which appears to retain macroscopic entropy even in the low-temperature limit where it enters a topological Coulomb phase. In the past seven years a new perspective has opened in the study of frustration through the creation of artificial frustrated magnetic systems. These materials consist of arrays of lithographically fabricated single-domain ferromagnetic nanostructures that behave like giant Ising spins. The nanostructures' interactions can be controlled through appropriate choices of their geometric properties and arrangement on a (frustrated) lattice. The degrees of freedom of the material can not only be directly tuned, but also individually observed. Experimental studies have unearthed intriguing connections to the out-of-equilibrium physics of disordered systems and nonthermal "granular" materials, while revealing strong analogies to spin ice materials and their fractionalized magnetic monopole excitations, lending the enterprise a distinctly interdisciplinary flavor. The experimental results have also been closely coupled to theoretical and computational analyses, facilitated by connections to classic models of frustrated magnetism, whose hitherto unobserved aspects have here found an experimental realization. Considerable experimental and theoretical progress in this field is reviewed here, including connections to other frustrated phenomena, and future vistas for progress in this rapidly expanding field are outlined.