论文标题
通过施加的磁场对单域粒子中磁化反转的最佳控制
Optimal control of magnetization reversal in a monodomain particle by means of applied magnetic field
论文作者
论文摘要
提出了一种完全分析解决方案，以示出了易于轴各向异性的大摩托蛋白的最佳逆转。确定逆转的能量成本的最佳控制路径被确定并用于得出最佳开关场的时间相关方向和振幅。反转尺度的最低能量成本与快速切换的切换时间相反，遵循指数的渐近级，用于缓慢开关，并达到与目标状态之间的能量屏障成正比的下限，并在无限长时间切换时间时与阻尼参数成正比。在给定的切换时间内，能源成本永远不会比免费的宏spin小。可以通过添加坚硬的各向异性轴来绕过该限制，该轴在所需的开关方向上激活内部扭矩，从而大大降低能源成本。计算出的最佳控制路径和最小能量路径之间的比较表明，最佳控制不能转化为能量屏障的最小化，而是表示有效利用系统的内部动力学来帮助所需的磁性转变。
A complete analytical solution to the optimal reversal of a macrospin with easy-axis anisotropy is presented. Optimal control path minimizing the energy cost of the reversal is identified and used to derive 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 an 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 which activates the internal torque in the desired switching direction, thereby significantly reducing the energy cost. 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.
