Anhui High Reliability Chips Engineering Laboratory, Hefei Innovation Research Institute, Beihang University, Hefei230013, China.
MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, Beijing100191, China.
ACS Appl Mater Interfaces. 2023 Feb 1;15(4):5608-5619. doi: 10.1021/acsami.2c19411. Epub 2023 Jan 23.
Manipulating magnetic skyrmions by means of a femtosecond (fs) laser pulse has attracted great interest due to their promising applications in efficient information-storage devices with ultralow energy consumption. However, the mechanism underlying the creation of skyrmions induced by an fs laser is still lacking. As a result, a key challenge is to reveal the pathway for the massive reorientation of magnetization from trivial to nontrivial topological states. Here, we studied a series of ferrimagnetic CoHo alloys and investigated the effect of a single laser pulse on the magnetic states. Thanks to the time-resolved magneto-optical Kerr effect and imaging techniques, we demonstrate that the laser-induced phase transitions from single domains into a topological skyrmion phase are mediated by the transient in-plane magnetization state, in real time and space domains, respectively. Combining experiments and micromagnetic simulations, we propose a two-step process for creating skyrmions through laser pulse irradiation: (i) the electron temperature enhancement induces a spin reorientation transition on a picosecond (ps) timescale due to the suppression of perpendicular magnetic anisotropy (PMA) and (ii) the PMA slowly restores, accompanied by out-of-plane magnetization recovery, leading to the generation of skyrmions with the help of spin fluctuations. This work provides a route to control skyrmion patterns using an fs laser, thereby establishing the foundation for further exploration of topological magnetism at ultrafast timescales.
由于在超低能耗的高效信息存储设备中具有广阔的应用前景，利用飞秒（fs）激光脉冲操控磁斯格明子引起了极大的关注。然而，飞秒激光诱导斯格明子产生的机制仍不明确。因此，一个关键的挑战是揭示从平凡拓扑态到非平凡拓扑态的磁化大规模重新取向的途径。在这里，我们研究了一系列亚铁磁 CoHo 合金，并研究了单个激光脉冲对磁态的影响。得益于时间分辨磁光克尔效应和成像技术，我们实时和空间域地证明了激光诱导的从单畴到拓扑斯格明子相的相变是通过瞬态的面内磁化状态来介导的。结合实验和微磁模拟，我们提出了一种通过激光脉冲辐照产生斯格明子的两步过程：（i）电子温度的增强由于抑制了垂直磁各向异性（PMA），在皮秒（ps）时间尺度上引起自旋重新取向转变；（ii）PMA 缓慢恢复，伴随着面外磁化的恢复，在自旋涨落的帮助下产生斯格明子。这项工作提供了一种利用飞秒激光控制斯格明子图案的方法，从而为在超快时间尺度上进一步探索拓扑磁学奠定了基础。
