The importance of the interface for picosecond spin pumping in antiferromagnet-heavy metal heterostructures.
The importance of the interface for picosecond spin pumping in antiferromagnet-heavy metal heterostructures.
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DOI：
10.1038/s41467-023-36166-z
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发表时间：
2023-02-01
影响因子：
16.6
通讯作者：
Ciccarelli, Chiara
中科院分区：
文献类型：
--
作者：
Kholid, Farhan Nur;Hamara, Dominik;Bin Hamdan, Ahmad Faisal;Antonio, Guillermo Nava;Bowen, Richard;Petit, Dorothee;Cowburn, Russell;Pisarev, Roman V.;Bossini, Davide;Barker, Joseph;Ciccarelli, Chiara
重金属(HM) -反铁磁绝缘体（AFI）异质结构中的界面最近成为高度研究和争论的系统，努力创造在太赫兹频率下工作的自旋电子器件。这种异质结构具有巨大的技术潜力，因为afi可以产生亚皮秒的自旋电流，而HMs可以将其转换为电荷信号。在这项工作中，我们利用时域太赫兹发射光谱证明了AFIs和Pt之间界面的光诱导皮秒自旋转移。我们选择了两个反铁磁体在同一个家族的氟立方钙钛矿，KCoF3和KNiF3，其磁振子频率在布里渊区中心相差一个数量级。通过研究它们随温度的行为，我们将界面上自旋转移效率的变化与低于nsamel温度的磁振子密度间隙的打开联系起来。我们的观察结果在一个基于反铁磁体中的局域电子和Pt中的自由电子之间的自旋交换的模型中得到了再现。通过对所选材料的比较研究，我们能够在皮秒时间尺度上对反铁磁体和重金属之间的自旋转移显微镜进行研究，并确定了其效率的关键数字：磁振子间隙。我们的研究结果对于从根本上理解HM/AFI界面的物理特性具有重要意义，这是设计具有优化特性的飞秒反铁磁自旋电子学器件的必要基石。通过将反铁磁体放置在重金属（如铂）旁边，反铁磁体中的磁激发会驱动重金属中的自旋电流，从而导致太赫兹辐射。在这里，Kholid等人研究了两种反铁磁体KCoF3和KNiF3的太赫兹发射，它们的磁振子频率非常不同，发现在态的磁振子密度中打开一个间隙会极大地改变自旋转移效率。
Interfaces in heavy metal (HM) - antiferromagnetic insulator (AFI) heterostructures have recently become highly investigated and debated systems in the effort to create spintronic devices that function at terahertz frequencies. Such heterostructures have great technological potential because AFIs can generate sub-picosecond spin currents which the HMs can convert into charge signals. In this work we demonstrate an optically induced picosecond spin transfer at the interface between AFIs and Pt using time-domain THz emission spectroscopy. We select two antiferromagnets in the same family of fluoride cubic perovskites, KCoF3 and KNiF3, whose magnon frequencies at the centre of the Brillouin zone differ by an order of magnitude. By studying their behaviour with temperature, we correlate changes in the spin transfer efficiency across the interface to the opening of a gap in the magnon density of states below the Néel temperature. Our observations are reproduced in a model based on the spin exchange between the localized electrons in the antiferromagnet and the free electrons in Pt. Through this comparative study of selected materials, we are able to shine light on the microscopy of spin transfer at picosecond timescales between antiferromagnets and heavy metals and identify a key figure of merit for its efficiency: the magnon gap. Our results are important for progressing in the fundamental understanding of the highly discussed physics of the HM/AFI interfaces, which is the necessary cornerstone for the designing of femtosecond antiferromagnetic spintronics devices with optimized characteristics. By placing an antiferromagnet next to a heavy metal such as platinum, magnetic excitations in the antiferromagnet drive a spin current in the heavy metal, leading to terahertz emission. Here, Kholid et al study the terahertz emission of two antiferromagnets, KCoF3 and KNiF3 with very different magnon frequencies, and find that the opening of a gap in the magnon density of states drastically alters the spin-transfer efficiency.
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