Fukumoto Keiki, Matsushita Tomohiro, Osawa Hitoshi, Nakamura Tetsuya, Muro Takayuki, Arai Kuniaki, Kimura Takashi, Otani Yoshichika, Kinoshita Toyohiko
SPring-8/JASRI, Sayo, Hyogo, Japan.
Rev Sci Instrum. 2008 Jun;79(6):063903. doi: 10.1063/1.2937648.
A femtosecond pulsed laser system has been installed at the BL25SU soft x-ray beamline at SPring-8 for time-resolved pump-probe experiments with synchronization of the laser pulses to the circularly polarized x-ray pulses. There are four different apparatuses situated at the beamline; for photoemission spectroscopy, two-dimensional display photoelectron diffraction, x-ray magnetic circular dichroism (XMCD) with electromagnetic coils, and photoelectron emission microscopy (PEEM). All four can be used for time-resolved experiments, and preliminary investigations have been carried out using the PEEM apparatus to observe magnetization dynamics in combination with XMCD. In this article, we describe the details of the stroboscopic pump-probe XMCD-PEEM experiment, and present preliminary data. The repetition rate of the laser pulses is set using a pulse selector to match the single bunches of SPring-8's hybrid filling pattern, which consists of several single bunches and a continuous bunch train. Electrons ejected during the bunch train, which do not provide time-resolved signal, are eliminated by periodically reducing the channel plate voltage using a custom-built power supply. The pulsed laser is used to create 300 ps long magnetic field pulses, which cause magnetic excitations in micron-sized magnetic elements which contain magnetic vortex structures. The observed frequency of the motion is consistent with previously reported observations and simulations.
一台飞秒脉冲激光系统已安装在日本兵库县播磨地区的SPring-8同步辐射装置的BL25SU软X射线光束线上，用于时间分辨泵浦-探测实验，实现激光脉冲与圆偏振X射线脉冲的同步。该光束线上有四种不同的仪器；分别用于光电子能谱、二维显示光电子衍射、带有电磁线圈的X射线磁圆二色性（XMCD）以及光电子发射显微镜（PEEM）。这四种仪器均可用于时间分辨实验，并且已经使用PEEM仪器结合XMCD对磁化动力学进行了初步研究。在本文中，我们描述了频闪泵浦-探测XMCD-PEEM实验的详细情况，并展示了初步数据。激光脉冲的重复频率通过脉冲选择器进行设置，以匹配SPring-8混合填充模式中的单个束团，该模式由几个单个束团和一个连续束团串组成。在束团串期间发射的电子不会提供时间分辨信号，通过使用定制电源周期性地降低通道板电压来消除这些电子。脉冲激光用于产生持续300 ps的磁场脉冲，这些脉冲会在包含磁涡旋结构的微米级磁性元件中引发磁激发。观察到的运动频率与先前报道的观察结果和模拟结果一致。
