Abstract We study the nonlinear gyrotropic motion of a magnetic skyrmion in a nanodisk by means of micromagnetic simulations. The skyrmion is driven by a linearly polarized harmonic field with the frequency of counterclockwise gyrotropic mode. It is found that the motion of the skyrmion displays different patterns with increasing field amplitude. In the linear regime of weak driving field, the skyrmion performs a single counterclockwise gyrotropic motion. The guiding center of the skyrmion moves along a helical line from the centre of the nanodisk to a stable circular orbit. The stable orbital radius increases linearly with the field amplitude. When the driving field is larger than a critical value, the skyrmion exhibits complex nonlinear motion. With the advance of time, the motion trajectory of the skyrmion goes through a series of evolution process, from a single circular motion to a bird nest-like and a flower-like trajectory and finally, to a gear-like steady-state motion. The frequency spectra show that except the counterclockwise gyrotropic mode, the clockwise gyrotropic mode is also nonlinearly excited and its amplitude increases with time. The complex motion trajectory of the skyrmion is the result of superposition of the two gyrotropic motions with changing amplitude. Both the linear and nonlinear gyrotropic motions of the skyrmion can be well described by a generalized Thiele’s equation of motion.

中文翻译：

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磁性纳米盘中斯格明子的非线性回旋运动

摘要 我们通过微磁模拟研究了纳米盘中磁性斯格明子的非线性回旋运动。斯格明子由线性极化谐波场驱动，频率为逆时针回旋模式。发现随着场幅的增加，斯格明子的运动表现出不同的模式。在弱驱动场的线性状态下，斯格明子执行单个逆时针陀螺运动。斯格明子的引导中心沿螺旋线从纳米盘中心移动到稳定的圆形轨道。稳定轨道半径随场幅度线性增加。当驱动场大于临界值时，斯格明子表现出复杂的非线性运动。随着时间的推移，斯格明子的运动轨迹经历了一系列的演化过程，从单一的圆周运动到鸟巢状和花朵状的运动轨迹，再到齿轮状的稳态运动。频谱表明，除逆时针回旋模式外，顺时针回旋模式也是非线性激发的，其幅度随时间增加。斯格明子的复杂运动轨迹是两种幅度变化的回旋运动叠加的结果。斯格明子的线性和非线性回旋运动都可以用广义的蒂勒运动方程很好地描述。顺时针回旋模式也是非线性激发的，其幅度随时间增加。斯格明子的复杂运动轨迹是两种幅度变化的回旋运动叠加的结果。斯格明子的线性和非线性回旋运动都可以用广义的蒂勒运动方程很好地描述。顺时针回旋模式也是非线性激发的，其幅度随时间增加。斯格明子的复杂运动轨迹是两种幅度变化的回旋运动叠加的结果。斯格明子的线性和非线性回旋运动都可以用广义的蒂勒运动方程很好地描述。