Unstable equilibrium point in chaotic domain-wall motion and Ott-Grebogi-Yorke control

A method for finding the unstable equilibrium points in Bloch wall motion i s proposed, which is important for controlling the chaotic domain-wall moti on by using the Ott-Grebogi-Yorke (OGY) method. The dynamics of Bloch wall motion are expressed by a nonlinear differential equation with the terms of inertia, damping, restoring, and an external magnetic drive force. An equa tion is transformed into the difference equations by following the OGY meth od, approximating linearly around an unstable equilibrium point (a saddle p oint), and adding a controlling input. The unstable equilibrium points are obtained by using the return map and the condition of hyperbolic fixed poin t. The time series of domain-wall motion successfully controlled on the uns table equilibrium points by the OGY method is shown. (C) 2001 American Inst itute of Physics.