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arXiv 1905.04034cond-mat.mes-hall
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几何约束Skyrmions的随机动力学和斑图形成

Stochastic dynamics and pattern formation of geometrically confined skyrmions

Alexander F. Schäffer, Levente Rózsa, Jamal Berakdar, Elena Y. Vedmedenko, Roland Wiesendanger

摘要:

系综的磁skyrmions在受限的几何形状表现出热驱动的运动在两个不同的时间尺度。内禀涨落动力学($t\sim 1~$ ps)由短程对称和反对称交换相互作用决定,而长时限($t\gtrsim10\,$ ns)由skyrmion-skyrmion-排斥和系统几何结构共同作用决定.微磁模拟现实岛屿的形状和大小进行和分析,表明在有限温度下的skyrmion动力学的特殊重要性。我们演示了skyrmion迁移率和观测时间之间的竞争如何直接影响skyrmion位的可寻址性,这是开发基于skyrmion的室温应用程序的道路上的一个关键挑战。所提出的准粒子蒙特卡罗方法提供了一个计算有效的描述skyrmion合奏的扩散运动在受限的几何形状,像跑道内存设置。

英文摘要:

Ensembles of magnetic skyrmions in confined geometries are shown to exhibit thermally driven motion on two different time scales. The intrinsic fluctuating dynamics ($t\sim 1~$ps) is governed by short-range symmetric and antisymmetric exchange interactions, whereas the long-time limit ($t\gtrsim10\,$ns) is determined by the coaction of skyrmion-skyrmion-repulsion and the system's geometry. Micromagnetic simulations for realistic island shapes and sizes are performed and analyzed, indicating the special importance of skyrmion dynamics at finite temperatures. We demonstrate how the competition between skyrmion mobility and observation time directly affects the addressability of skyrmionic bits, which is a key challenge on the path of developing skyrmion-based room-temperature applications. The presented quasiparticle Monte Carlo approach offers a computationally efficient description of the diffusive motion of skyrmion ensembles in confined geometries, like racetrack memory setups.

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