Optimal Control of Magnetization Reversal in a Monodomain Particle by Means of Applied Magnetic Field

A complete analytical solution to the optimal reversal of a macrospin with easy-axis anisotropy is presented. Optimal control path minimizing energy cost identified and used derive time-dependent direction amplitude switching field. The minimum scales inversely time for fast switching, follows an exponential asymptotics slow reaches lower limit proportional barrier between target states damping parameter at infinitely long time. For given time, never smaller than that free macrospin. This limitation can be bypassed by adding hard axis which activates internal torque in desired direction, thereby significantly reducing cost. Comparison calculated reveals does not translate minimization barrier, but signifies effective use system's dynamics aid magnetic transition.