  Input-driven dynamical systems have attracted attention because their
dynamics can be used as resources for brain-inspired computing. The recent
achievement of human-voice recognition by spintronic oscillator also utilizes
an input-driven magnetization dynamics. Here, we investigate an excitation of
input-driven chaos in magnetization dynamics by voltage controlled magnetic
anisotropy effect. The study focuses on the parametric magnetization
oscillation induced by a microwave voltage and investigates the effect of
random-pulse input on the oscillation behavior. Solving the
Landau-Lifshitz-Gilbert equation, temporal dynamics of the magnetization and
its statistical character are evaluated. In a weak perturbation limit, the
temporal dynamics of the magnetization are mainly determined by the input
signal, which is classified as input-driven synchronization. In a large
perturbation limit, on the other hand, chaotic dynamics are observed, where the
dynamical response is sensitive to the initial state. The existence of chaos is
also identified by the evaluation of the Lyapunov exponent.
