通过X射线磁圆二色性实现全光磁化反转
All-optical magnetization reversal via x-ray magnetic circular dichroism
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中文总结 AI 辅助
利用X射线磁圆二色性，通过圆偏振硬X射线实现Pt/Co/Pt多层结构的全光磁化反转。
中文摘要 AI 辅助
光的偏振是最重要的基本特性之一，等同于能量和相干性。磁性会改变光的偏振，反之亦然。将强的圆偏振飞秒脉冲照射到磁性材料上可以改变磁序和基本激发态，特别是在可见到近红外波长范围内。此外，最近X射线自由电子激光的发展使能够以高时间和空间分辨率追踪超快动力学的元素特异性动态成为可能。然而，X射线光子的偏振手性尚未被用来控制凝聚态材料的序参量，不仅限于磁现象。在此，我们展示了通过照射飞秒圆偏振硬X射线脉冲，仅对Pt/Co/Pt多层结构进行确定性的磁化反转。观察到的全光磁化反转依赖于入射X射线脉冲的手性和在Pt L3边的光子能量强烈共振。这些结果源于Pt的X射线磁圆二色性，涉及由于与Co的磁近邻效应，手性依赖的从2p3/2核心能级到交换分裂的5d价态的激发。这些发现标志着在X射线区域研究光与物质相互作用的新前沿。
英文摘要
Light polarization is one of the most fundamental features, equivalent to energy and coherence. Magnetism changes light polarization, and vice versa. The irradiation of intense circularly polarized femtosecond pules to magnetic materials can alter the magnetic orders and elementary excitations, particularly in the visible to infrared spectral regions. Furthermore, the recent development of x-ray free-electron laser enables the element-specific trace of the ultrafast dynamics with high time and spatial resolution. However, the light helicity of x-ray photons has not yet been used to control order parameters in condensed matter materials, not limited to such magnetic phenomenon. Here, we demonstrate the deterministic magnetization reversal of a ferromagnetic Pt/Co/Pt multilayer solely by irradiating femtosecond pulses of circularly polarized hard x-rays. The observed all-optical magnetization switching depends on the helicity of incident x-ray pulses and is strongly resonant with the photon energy at the Pt $L_3$ edge. These results originate in the x-ray magnetic circular dichroism of Pt, involving helicity-dependent excitation from the 2$p_{3/2}$ core level to the exchange-split 5$d$ valence states owing to the magnetic proximity effect with Co. These findings mark a new frontier for examining interactions between light and matter in the x-ray region.
