Breathing modes of confined skyrmions in ultrathin magnetic dots

The dynamics of individual magnetic skyrmions confined in ultrathin film dots is studied theoretically. The systems considered are transition-metal ferromagnets possessing perpendicular magnetic anisotropy and particular attention is given to the dynamic response of the skyrmions to perpendicular ac fields. By using micromagnetics simulations, it is shown that breathing modes can hybridize with geometrically quantized spin wave eigenmodes of the circular dots, leading to distinct features in the power spectrum that differ from the behavior expected for uniformly magnetized systems. The static field dependence of the breathing mode frequency offers a direct means of detecting and characterizing such skyrmion states in experiment.