Strong high-frequency spin waves released periodically from a confined region Zhen-Wei Zhou, Xi-Guang Wang, Yao-Ghuang Nie, Qing-Lin Xia and Guang-Hua Guo Eur. Phys. J. Appl. Phys., 91 3 (2020) 30601 Published online: 10 September 2020 DOI: 10.1051/epjap/2020200144