Directional dependence of vortex core resonance in a square-shaped ferromagnetic dot

• The dynamic property of a magnetic vortex confined in a square ferromagnetic dot has been investigated.
• The field dependence of the resonant property strongly depends on the direction of the magnetic field.
• The resonant frequency is strongly modified by the magnetic field along the diagonal direction of the square.

The resonant property of the magnetic vortex confined in a square-shaped ferromagnetic dot has been investigated. We showed that the field dependence of the resonant frequency has a unique directional dependence originating from a four-fold rotational symmetry of the square. The resonant frequency is found to be strongly modulated by the magnetic field along the diagonal direction although the magnetic field applied along the side of the square hardly modified the resonant frequency. The modulation ratio of the resonant frequency defined by the ratio between minimum and maximum frequencies for the vortex resonance was found to be tuned by the lateral dimension of the square. These unique frequency tunabilities controlled by the magnitude and the direction of the magnetic field may provide additional functions in the application of the magnetic vortex systems.