Complex dynamics in unidirectionally coupled overdamped bistable systems subject to a time-periodic external signal.

Recently, we have studied the emergence of oscillatory behavior in overdamped undriven nonlinear dynamic systems subject to carefully crafted coupling schemes and operating conditions [V. In, Phys. Rev. E 68, 045102(R) (2003).] The theoretical ideas have been validated in an experimental setup of N = 3 coupled ferromagnetic cores subject to a dc external magnetic "target" signal; the oscillations (corresponding to the periodic switching of each core between its stable steady states of magnetization) are triggered when the coupling constant crosses a threshold value, with the oscillation frequency exhibiting a characteristic scaling behavior with the "separation" of the coupling constant from its threshold value, as well as with the external signal amplitude. Here, we consider the system response to a time-periodic signal. We demonstrate experimentally that, depending on the signal amplitude and frequency, the response can be either synchronized to the signal frequency or to one-third this frequency. These phenomena afford unique techniques for time-periodic signal detection and characterization for a large class of sensors.