2020/04/21 by G. J. Kwiatkowski, Grzegorz Kwiatkowski, M. H. A. Badarneh +5 · 9 citations
Materials Science · Physics and Astronomy · #Condensed matter physics #Magnetic Properties and Applications #Magnetic anisotropy #Magnetic field #Magnetic hysteresis #Magnetic particle inspection #Magnetic properties of thin films #Magnetization #Magnetization reversal #Materials science #Particle (ecology) #Physics #Quantum mechanics #Single domain #Stoner–Wohlfarth model #cond-mat.mes-hall #stochastic dynamics and bifurcation
paper · pdf · doi:10.1103/physrevlett.126.177206
published in Physical Review Letters 126(17), 177206 (American Physical Society)
arxiv created 2020/04/21 · openalex publication_date 2021/04/29 · arxiv updated 2021/05/05 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
A complete analytical solution to the optimal reversal of a macrospin with easy-axis anisotropy is presented. An optimal control path minimizing the energy cost of the reversal is identified and used to derive the time-dependent direction and amplitude of the optimal switching field. The minimum energy cost of the reversal scales inversely with the switching time for fast switching, follows exponential asymptotics for slow switching, and reaches the lower limit proportional to the energy barrier between the target states and to the damping parameter at infinitely long switching time. For a given switching time, the energy cost is never smaller than that for a free macrospin. This limitation can be bypassed by adding a hard anisotropy axis that activates the internal torque in the desired switching direction, thereby significantly reducing the energy cost. A comparison between the calculated optimal control path and minimum energy path reveals that optimal control does not translate to the minimization of the energy barrier but signifies effective use of the system's internal dynamics to aid the desired magnetic transition.