Spin eigenmodes of skyrmion bags

Abstract Recently, magnetic skyrmion bags have been numerically and experimentally discovered in a thick FeGe plate. Here, we systematically investigated the spin eigenmodes of skyrmion bags in a confined magnetic disk. A weak peak at lower frequency is found for the skyrmion bags with Q ≠ 0 rather than skyrmionium due to the reduced rotational symmetry. In addition, it is found that a lot of spin eigenmodes for skyrmion bags which are more complex than the breathing mode of ordinary skyrmion can also be excited due to the inner interaction between skyrmions. Afterward, the spin eigenmodes at different external fields as well as in different disk sizes are further investigated. The results reveal rich physical phenomena and help us understand the interactions between skyrmions well. In addition, it can also be used as a detection and characterization mechanism for skyrmion bags.