Magneto‐ionics, as the electrochemical reconfiguration of magnetic materials at low gating voltages, is a highly energy‐efficient alternative to control magnetism. For the fastest magneto‐ionic concept based on hydrogen, fundamental mechanisms are currently under debate, mainly because quantitative compositional information inside the magnetic materials upon gating is lacking. Using the electrochemical hydrogen loading of Co/Pd multilayers with perpendicular anisotropy, this study demonstrates that the hydrogen concentration inside the magnetic material determines its magnetic properties. Hydrogen concentrations up to a maximum of (0.24 ± 0.01) hydrogen atoms per metal atom can be set deterministically by voltage and are quantified via flow‐cell coulometry. With increasing hydrogen concentration, a continuous increase in coercivity of up to 15% and a decrease in magnetic domain‐wall velocity by an order of magnitude are observed using in situ MOKE microscopy. This enables the voltage‐controlled stop‐and‐go of domain walls. These magneto‐ionic effects can be explained by an increasing perpendicular anisotropy with increasing hydrogen content in Co/Pd multilayers, which is supported by theory. Importantly, the approach should be transferable to other ionic systems, such as lithium‐ or oxygen‐based ones, where it can uncover the yet hidden effects of ionic concentration on the magnetic properties and guide the design of functional magneto‐ionic devices.

中文翻译：

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通过电化学氢负载对 Co/Pd 多层膜中的矫顽力和畴壁速度进行磁离子控制


磁离子学作为磁性材料在低选通电压下的电化学重构，是控制磁性的一种高能效替代方案。对于基于氢的最快磁离子概念，其基本机制目前仍在争论中，主要是因为缺乏门控时磁性材料内部的定量成分信息。这项研究利用具有垂直各向异性的 Co/Pd 多层膜的电化学氢负载，证明磁性材料内部的氢浓度决定其磁性能。每个金属原子最多 (0.24 ± 0.01) 个氢原子的氢浓度可以通过电压确定性地设置，并通过流通池库仑法进行量化。随着氢浓度的增加，使用原位 MOKE 显微镜观察到矫顽力持续增加高达 15%，磁畴壁速度降低一个数量级。这使得畴壁的电压控制停止和运行成为可能。这些磁离子效应可以通过 Co/Pd 多层中氢含量增加而增加的垂直各向异性来解释，这一点得到了理论的支持。重要的是，该方法应该可以转移到其他离子系统，例如锂基或氧基系统，它可以揭示离子浓度对磁性能的隐藏影响，并指导功能性磁离子器件的设计。