Time-Delayed Feedback Method to Control Magnetic Orientation Dynamics in a Driven Anisotropic Nanoparticle System(Condensed Matter and Statistical Physics)

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This paper proposes a theoretical method for control to switch the dynamics of the mean magnetic moment of a nanoparticle from a state of being (anti-)parallel to the magnetic easy axis into a state of swinging oscillation across the plane perpendicular to the anisotropic axis, or from the latter oscillation to the former state. The magnetic system is described as a single classical magnetic moment governed by a Landau-Lifshitz-type equation with a Gilbert damping term, and it is simplified by ignoring the magnetic effects other than the magnetic anisotropy and the driving magnetic field in order to externally control the mean magnetic moment. The driving field consists of a sinusoidal field and a controlling field which is implemented by a time-delayed feedback scheme in order to stabilize an unstable periodic cycle of the driven magnetic moment. First, we show the possibility for control with a conventional delayed-feedback scheme and we discuss the domains of relevant parameters for its linear stability in some cases in which the conversion from an internal physical state to measurable quantity is given by a linear transform, or that includes a weak nonlinearity. Then, we present one example of an extended control method to improve the stabilization so that it works better even in a driving field that is of lower frequency than that treated in the first part.
理論物理学刊行会の論文
2006-12-25