ISSP Stay report of Prof. Byong-Guk Park
Byong-Guk Park
KAIST
I had the great pleasure of visiting the group of Professor Shinji Miwa at the Institute for Solid State Physics (ISSP), the University of Tokyo, for four months. Prior to joining KAIST, I worked at the Hitachi Cambridge Laboratory in the UK and had the opportunity to visit Tokyo on a yearly basis. However, this was my first extended stay in Japan. During this period, I was able to gain a deeper understanding of both Japanese daily life and research culture, which made this visit particularly meaningful.
During my four-month stay, I participated in two research projects in the Miwa group. The first project, carried out in collaboration with Jieyi Chen, focused on the orbital torque generated in single-crystalline Ti and its crystallographic orientation dependence. This work took advantage of the Miwa group’s advanced molecular beam epitaxy (MBE) capabilities, which enabled us to grow high-quality single-crystalline Ti (110) thin films on MgO substrates. We quantified the orbital torques generated in Ti and exerted on adjacent ferromagnetic layers (Ni and NiFe) using harmonic Hall measurements. These experiments were conducted in collaboration with my KAIST group member. The preliminary results revealed that the torque arising from the orbital current exhibits a clear dependence on the crystallographic direction. Furthermore, we observed a non-negligible torque component along the x-direction at certain crystal orientations, which has not been previously reported and suggests the presence of additional mechanisms requiring further investigation. This research has continued even after my return to Korea. The second project, conducted in collaboration with Xiaoyu Piao, aimed to quantify spin currents generated in antiferromagnetic NiO using spin diode effects. This study was carried out using the well-established ST-FMR measurement technique developed in the Miwa group. The experimental measurements have been completed, and the data are currently under analysis.
Following this visit, I would like to continue collaborative research on both topics with the Professor Miwa group. Furthermore, I hope this visit will serve as a starting point for establishing a Korea–Japan collaborative platform in spintronics to promote sustained research collaboration and academic exchange.
In addition to my research, I actively engaged in academic exchanges during my stay. First I delivered a keynote talk at ‘International Symposium on Spintronics with Antiferromagents and Altermagnets’, and I co-organized the ISSP workshop ‘Spintronics Future Prospects’ with Prof. Miwa, where we invited outstanding researchers from Japan, Korea, and China to discuss future directions in spintronic research. Furthermore, I gave six invited seminars at major universities and research institutes, including AIST, Tohoku University, NIMS, Osaka University, the University of Tokyo, and Kyoto University. These presentations that focused on spin–orbit torque physics and their potential applications provided valuable opportunities for scientific discussion and collaboration.
Last, but not least, I would like to sincerely thank Ms. Yuko Ishiguchi of the International Liaison Office at ISSP for making my visit as smooth as possible. I am deeply grateful for her time and effort she devoted to helping me enjoy a comfortable and pleasant stay in Japan. I also sincerely appreciate the support and hospitality of Professor Shinji Miwa’s group members, including Ms. Yukiko Kato and the students, whose collaboration and discussions were invaluable throughout my stay. I look forward to continuing our collaboration and visiting ISSP again in the near future.
