简谐振荡梯度磁场中悬浮单畴纳米粒子的漂移
Drift of suspended single-domain nanoparticles in a harmonically oscillating gradient magnetic field
摘要：
研究了在均匀磁场存在和不存在的情况下，在谐振荡梯度磁场作用下，单畴铁磁纳米颗粒在粘性液体中的非线性动力学行为。在一些物理上合理的假设下，我们推导出一组耦合的刚性常微分方程的磁化角和粒子坐标描述的旋转和平移运动的纳米粒子。这些方程的解析解被确定为纳米粒子附近和远离坐标原点，并证实其正确性数值。我们发现，如果没有一个均匀的磁场，每个纳米粒子的磁化角和粒子坐标是时间的周期函数。相反，均匀磁场的存在使得这些函数是非周期性的。在这种情况下，我们对纳米颗粒动力学进行了详细的分析，并预测了纳米颗粒漂移运动（定向运输）的出现。我们用解析和数值方法计算了漂移速度，研究了漂移速度与时间和模型参数的关系，分析了漂移现象的物理起源，并讨论了其潜在的生物医学应用。
英文摘要：
We study the nonlinear dynamics of single-domain ferromagnetic nanoparticles in a viscous liquid induced by a harmonically oscillating gradient magnetic field in the absence and presence of a static uniform magnetic field. Under some physically reasonable assumptions, we derive a coupled set of stiff ordinary differential equations for the magnetization angle and particle coordinate describing the rotational and translational motions of nanoparticles. Analytical solutions of these equations are determined for nanoparticles near and far from the coordinate origin, and their correctness is confirmed numerically. We show that if a uniform magnetic field is absent, the magnetization angle and particle coordinate of each nanoparticle are periodic functions of time. In contrast, the presence of a uniform magnetic field makes these functions aperiodic. In this case, we perform a detailed analysis of the nanoparticle dynamics and predict the appearance of the drift motion (directed transport) of nanoparticles. We calculate both analytically and numerically the drift velocity, study its dependence on time and model parameters, analyze the physical origin of the drift phenomenon and discuss its potential biomedical applications.
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