Guo J, Ghosh P, Hill D, Chen Y, Stingaciu L, Zolnierczuk P, Ullrich C A, Singh D K
Department of Physics and Astronomy, University of Missouri, Columbia, MO, USA.
Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou, China.
Nat Commun. 2023 Aug 25;14(1):5212. doi: 10.1038/s41467-023-41003-4.
Topological magnetic charges, arising due to the non-vanishing magnetic flux on spin ice vertices, serve as the origin of magnetic monopoles that traverse the underlying lattice effortlessly. Unlike spin ice materials of atomic origin, the dynamic state in artificial honeycomb spin ice is conventionally described in terms of finite size domain wall kinetics that require magnetic field or current application. Contrary to this common understanding, here we show that a thermally tunable artificial permalloy honeycomb lattice exhibits a perpetual dynamic state due to self-propelled magnetic charge defect relaxation in the absence of any external tuning agent. Quantitative investigation of magnetic charge defect dynamics using neutron spin echo spectroscopy reveals sub-ns relaxation times that are comparable to the relaxation of monopoles in bulk spin ices. Most importantly, the kinetic process remains unabated at low temperature where thermal fluctuation is negligible. This suggests that dynamic phenomena in honeycomb spin ice are mediated by quasi-particle type entities, also confirmed by dynamic Monte-Carlo simulations that replicate the kinetic behavior. Our research unveils a macroscopic magnetic particle that shares many known traits of quantum particles, namely magnetic monopole and magnon.
由于自旋冰顶点上存在非零磁通量而产生的拓扑磁荷，是轻松穿越底层晶格的磁单极子的起源。与原子起源的自旋冰材料不同，人工蜂窝状自旋冰中的动态状态通常根据需要施加磁场或电流的有限尺寸畴壁动力学来描述。与这种普遍认识相反，我们在此表明，一种热可调谐的人工坡莫合金蜂窝晶格在没有任何外部调谐剂的情况下，由于自推进磁荷缺陷弛豫而呈现出永久动态状态。使用中子自旋回波光谱对磁荷缺陷动力学进行的定量研究揭示了亚纳秒级的弛豫时间，这与体自旋冰中磁单极子的弛豫时间相当。最重要的是，在热涨落可忽略不计的低温下，动力学过程仍未减弱。这表明蜂窝状自旋冰中的动态现象是由准粒子类型的实体介导的，动态蒙特卡罗模拟也证实了这一点，该模拟重现了动力学行为。我们的研究揭示了一种宏观磁性粒子，它具有许多已知的量子粒子特性，即磁单极子和磁振子。
