Controlled Stochastic Resonance in a Bistable Magnetic System(General and Mathamatical Physics)

概要

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A controlled stochastic resonance (SR) with a time-delayed feedback control scheme is studied with a model of bistable magnetic system. The model is given by a stochastic Landau-Lifshitz-Gilbert equation with a sinusoidal field and a time-delayed feedback input field, which regulates SR by feedbacking the delayed state whose delay time equals the half-period of the sinusoidal field. The effect of SR is characterized by power consumption (PC) by the sinusoidal field, which is proportional to the imaginary part of dynamic susceptibility. It is found that the PC exhibits a double-peak structure for two distinctive noise intensities under a certain condition, and that the first peak is relevant to a conventional SR mechanism, but the second is a new one due to the feedback. Around the second peak, one can observe a change in dynamics from a phase-slipping state to a phase-locked state as the noise intensity increases to the second peak point from the minimum point of the PC. The realization of the phase-locked state, in which the motion of the magnetization vector entrains to the sinusoidal field, reminds us of a ratchetlike mechanism. In this paper, an analytic expression of the dynamic susceptibility is obtained from a dichotomic model, which is deduced from the original Fokker-Planck equation.
2010-01-25