Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120, Uppsala, Sweden.
1] Laboratory for Micro- and Nanotechnology, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland [2] Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, CH-8093 Zurich, Switzerland.
Nat Nanotechnol. 2014 Jul;9(7):514-9. doi: 10.1038/nnano.2014.104. Epub 2014 Jun 8.
Artificial spin ice systems have been proposed as a playground for the study of monopole-like magnetic excitations, similar to those observed in pyrochlore spin ice materials. Currents of magnetic monopole excitations have been observed, demonstrating the possibility for the realization of magnetic-charge-based circuitry. Artificial spin ice systems that support thermal fluctuations can serve as an ideal setting for observing dynamical effects such as monopole propagation and as a potential medium for magnetricity investigations. Here, we report on the transition from a frozen to a dynamic state in artificial spin ice with a square lattice. Magnetic imaging is used to determine the magnetic state of the islands in thermal equilibrium. The temperature-induced onset of magnetic fluctuations and excitation populations are shown to depend on the lattice spacing and related interaction strength between islands. The excitations are described by Boltzmann distributions with their factors in the frozen state relating to the blocking temperatures of the array. Our results provide insight into the design of thermal artificial spin ice arrays where the magnetic charge density and response to external fields can be studied in thermal equilibrium.
人工自旋冰系统被提议作为研究单磁激发的实验平台，类似于在方钴矿自旋冰材料中观察到的单磁激发。已经观察到磁单极子激发的电流，这证明了基于磁荷的电路实现的可能性。支持热涨落的人工自旋冰系统可以作为观察单极子传播等动力学效应的理想环境，并且可能是磁性研究的潜在介质。在这里，我们报告了在具有正方形晶格的人工自旋冰中从冻结态到动态态的转变。磁成像用于确定在热平衡时的岛的磁状态。结果表明，温度引起的磁涨落和激发态种群取决于晶格间距以及岛之间的相关相互作用强度。这些激发态可以用玻尔兹曼分布来描述，在冻结态下，其因子与数组的阻挡温度有关。我们的研究结果为热人工自旋冰阵列的设计提供了新的思路，其中可以在热平衡时研究磁电荷密度和对外场的响应。
