Spintronic terahertz (THz) emission via spin-to-charge conversion (SCC) has been widely studied in ferromagnets (FM)/nonmagnets (NM) structures, in which various mechanisms of SCC have been confirmed in different NM materials. However, it is rare to find a material having multiple SCC mechanisms at the same time. Here, we report a ferromagnetic metal Ni film with diverse functions in the SCC process, by performing THz emission experiments in single Ni layer, FM/Ni, Ni/NM bilayers and FM/Ni/NM trilayers. It is demonstrated that in Ni monolayer, THz emission is radiated by the anomalous Hall effect and ultrafast demagnetization of Ni film. In FM/Ni, the Ni film acts as an SCC implementer and THz emission is mainly generated by the inverse spin Hall effect (ISHE) of Ni. In Ni/NM, the Ni film acts as a spin injector and provides spin currents to be converted to charge current via ISHE of heavy metal NM, inducing THz emission. In FM/Ni/NM, THz emission mainly comes from ISHE of FM/Ni, Ni/NM, and FM/NM, and their domination is relative to Ni thickness. Our findings show a ferromagnetic film not only acts as a spin injector but also as an SCC implementer, providing a new concept to design spintronic THz emitters.

中文翻译：

---

铁磁镍纳米薄膜中的太赫兹自旋电荷转换

通过自旋到电荷转换 (SCC) 的自旋电子太赫兹 (THz) 发射已在铁磁体 (FM)/非磁体 (NM) 结构中得到广泛研究，其中 SCC 的各种机制已在不同的 NM 材料中得到证实。然而，很难找到同时具有多种 SCC 机制的材料。在这里，我们通过在单个 Ni 层、FM/Ni、Ni/NM 双层和 FM/Ni/NM 三层中进行 THz 发射实验，报告了一种在 SCC 过程中具有多种功能的铁磁金属 Ni 薄膜。结果表明，在镍单层中，太赫兹发射是由镍薄膜的异常霍尔效应和超快退磁辐射出来的。在 FM/Ni 中，Ni 薄膜充当 SCC 实现者，THz 发射主要由 Ni 的逆自旋霍尔效应 (ISHE) 产生。在镍/纳米，镍膜充当自旋注入器并提供自旋电流，通过重金属 NM 的 ISHE 转换为充电电流，从而诱导太赫兹发射。在FM/Ni/NM中，太赫兹发射主要来自FM/Ni、Ni/NM和FM/NM的ISHE，其主导地位与Ni厚度有关。我们的研究结果表明，铁磁薄膜不仅充当自旋注入器，而且充当 SCC 实施者，为设计自旋电子太赫兹发射器提供了新概念。