Optical Creation of Skyrmions by Spin Reorientation Transition in Ferrimagnetic CoHo Alloys

• Published in: ACS applied materials & interfaces 2023-02, Vol.15 (4), p.5608-5619
• Main Authors: Zhang, Wei, Huang, Tian Xun, Hehn, Michel, Malinowski, Grégory, Verges, Maxime, Hohlfeld, Julius, Remy, Quentin, Lacour, Daniel, Wang, Xin Ran, Zhao, Guo Ping, Vallobra, Pierre, Xu, Yong, Mangin, Stéphane, Zhao, Wei Sheng
• Format: Article
• Language: English
• Subjects: Condensed Matter; Functional Nanostructured Materials (including low-D carbon); Physics
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.2c19411

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.