Terahertz spin current pulses controlled by magnetic heterostructures
Terahertz spin current pulses controlled by magnetic heterostructures
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DOI：
10.1038/nnano.2013.43
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发表时间：
2013-04-01
影响因子：
38.3
通讯作者：
Muenzenberg, M.
中科院分区：
文献类型：
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作者：
Kampfrath, T.;Battiato, M.;Muenzenberg, M.
在基于自旋的电子学中，信息由电子束团（1-4）的自旋状态编码。处理这些信息需要通过固体（5，6）控制自旋角动量的传输，最好是在达到迄今为止未探索的太赫兹范围（7-9）的频率下。在这里，我们证明，通过实验和理论，飞秒自旋电流爆发的时间形状可以通过使用专门设计的磁性异质结构来操纵。激光脉冲用于将自旋（10-12）从铁磁性铁薄膜驱动到具有低（钌）或高（金）电子迁移率的非磁性盖层中。通过基于逆自旋霍尔效应（14，15）的超快非接触式电流计（13）检测所产生的瞬态自旋电流，该电流计将自旋流转换成太赫兹电磁脉冲。我们发现钌帽层产生相当长的自旋电流脉冲，因为电子被注入钌d态，其具有比金sp态低得多的迁移率（16）。因此，自旋电流脉冲和由此产生的太赫兹瞬态可以通过定制磁性异质结构来成形，这为设计高速自旋电子器件和潜在的宽带太赫兹发射器打开了大门（7-9）。
In spin-based electronics, information is encoded by the spin state of electron bunches(1-4). Processing this information requires the controlled transport of spin angular momentum through a solid(5,6), preferably at frequencies reaching the so far unexplored terahertz regime(7-9). Here, we demonstrate, by experiment and theory, that the temporal shape of femtosecond spin current bursts can be manipulated by using specifically designed magnetic heterostructures. A laser pulse is used to drive spins(10-12) from a ferromagnetic iron thin film into a non-magnetic cap layer that has either low (ruthenium) or high (gold) electron mobility. The resulting transient spin current is detected by means of an ultrafast, contactless amperemeter(13) based on the inverse spin Hall effect(14,15), which converts the spin flow into a terahertz electromagnetic pulse. We find that the ruthenium cap layer yields a considerably longer spin current pulse because electrons are injected into ruthenium d states, which have a much lower mobility than gold sp states(16). Thus, spin current pulses and the resulting terahertz transients can be shaped by tailoring magnetic heterostructures, which opens the door to engineering high-speed spintronic devices and, potentially, broadband terahertz emitters(7-9).