  Hysteresis dispersion under a varying external field Hex is investigated
through numerical simulations based on the Landau-Lifshitz-Gilbert (LLG)
equation, indicating the energy dissipation can be determined by W({\eta}) = A
(f, H0). A linear relation between area of hysteresis and magnitude of external
field is discovered. Evolution of hysteresis is also investigated under
oscillating external field.
