Superferromagnetism and Domain-Wall Topologies in Artificial "Pinwheel" Spin Ice
Superferromagnetism and Domain-Wall Topologies in Artificial "Pinwheel" Spin Ice
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DOI：
10.1021/acsnano.8b08884
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发表时间：
2019-02-01
期刊：
影响因子：
17.1
通讯作者：
Stamps, Robert L.
中科院分区：
文献类型：
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作者：
Li, Yue;Paterson, Gary W.;Stamps, Robert L.
十多年来，相互作用的单畴纳米磁体阵列，被称为人工自旋冰，已经被设计用于研究模型自旋系统中的挫折。在这里，我们使用菲涅尔成像研究反转过程中的“风车”人工自旋冰，一个修改后的方形ASI结构，通过旋转每个岛屿的中点，以一定的角度获得。我们的研究结果表明，一个简单的45旋转的磁顺序从反铁磁到铁磁的变化，创造一个超铁磁体，表现出介导的畴壁成核和相干畴传播的介观畴生长。我们观察到几个畴壁配置，其中大多数是直接类似于连续铁磁薄膜中看到的。然而，由于系统的几何约束，带电壁也会出现。改变外部磁场的方向可以控制自旋反转的性质，从而出现一维或二维的雪崩。风车ASI的这种性质可以用于调谐基于磁输运现象的器件，例如霍尔电路。
For over ten years, arrays of interacting single-domain nanomagnets, referred to as artificial spin ices, have been engineered with the aim to study frustration in model spin systems. Here, we use Fresnel imaging to study the reversal process in "pinwheel" artificial spin ice, a modified square ASI structure obtained by rotating each island by some angle about its midpoint. Our results demonstrate that a simple 45 rotation changes the magnetic ordering from antiferromagnetic to ferromagnetic, creating a superferromagnet which exhibits mesoscopic domain growth mediated by domain wall nucleation and coherent domain propagation. We observe several domain-wall configurations, most of which are direct analogues to those seen in continuous ferromagnetic films. However, charged walls also appear due to the geometric constraints of the system. Changing the orientation of the external magnetic field allows control of the nature of the spin reversal with the emergence of either one- or two-dimensional avalanches. This property of pinwheel ASI could be employed to tune devices based on magnetotransport phenomena such as Hall circuits.