Spin current is a crucial element in spintronics, and its diffusion in materials is typically characterized by monotonic decay. However, when the material hosting the spin current is also a magnet, the spin current is expected to exhibit spatial oscillations, the observation of which remains elusive. Here, we demonstrate the spatial oscillation of a spin current in a nickel film by measuring the thickness-dependent inverse spin Hall effect in $\mathrm{Ni}/\mathrm{YIG}$ bilayers. The inverse spin Hall current in nickel is found to oscillate with its film thickness, in contrast to nonmagnetic materials, and that the oscillation period quantitatively agrees with theoretical predictions based on differences in the Fermi wave vector between majority and minority carriers. Our findings reveal a previously hidden behavior of spin-transport dynamics and identify a new degree of freedom for manipulating spin current, with potential implications for future spintronic devices.

中文翻译：

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铁磁体中自旋电流振荡的直接观察


自旋流是自旋电子学中的关键元素，其在材料中的扩散通常具有单调衰减的特征。然而，当承载自旋流的材料也是磁体时，自旋流预计会表现出空间振荡，但对其观察仍然难以捉摸。在这里，我们通过测量 $\mathrm{Ni}/\mathrm{YIG}$ 双层中厚度相关的逆自旋霍尔效应来演示镍膜中自旋电流的空间振荡。与非磁性材料相比，镍中的反自旋霍尔电流被发现随其薄膜厚度而振荡，并且振荡周期在数量上与基于多数载流子和少数载流子之间的费米波矢量差异的理论预测一致。我们的研究结果揭示了自旋输运动力学先前隐藏的行为，并确定了操纵自旋电流的新自由度，对未来的自旋电子器件具有潜在影响。