Simulation and Quantitative Clarification of AC Susceptibility of Magnetic Fluid in Nonlinear Brownian Relaxation Region
Simulation and Quantitative Clarification of AC Susceptibility of Magnetic Fluid in Nonlinear Brownian Relaxation Region
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DOI：
10.1143/jjap.48.127002
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发表时间：
2009-12-01
影响因子：
1.5
通讯作者：
Enpuku, Keiji
中科院分区：
文献类型：
--
作者：
Yoshida, Takashi;Enpuku, Keiji
研究了磁流体在大激励场下的非线性布朗转动弛豫与其生物医学应用的关系。采用数值模拟的方法求解了描述磁流体非线性行为的Fokker-Planck方程，分别在大台阶和正弦磁场作用下求解。偏离德拜理论定量澄清。首先，它表明，磁流体的响应时间变得短于布朗弛豫时间为一个更大的激发场，这可以表示在依赖于场的布朗弛豫时间。接下来，交流磁化率的振幅变得更低的激发场，和交流磁化率的频率特性移动到一个更高的频率相比，由德拜理论预测。最后，随着激励场的增加，出现了高次谐波。近似方程，描述这种非线性行为相当不错，也得到了。这些方程有望用于开发基于布朗弛豫的生物传感器。(C)2009日本应用物理学会
The nonlinear Brownian rotational relaxation of magnetic fluids for the case of large excitation field was studied in relation to its biomedical applications. The Fokker-Planck equation, which describes the nonlinear behavior of magnetic fluids, was solved by numerical simulation when a large step or a sinusoidal field was applied. Deviations from the Debye theory were quantitatively clarified. First, it was shown that the response time of the magnetic fluids became shorter than the Brownian relaxation time for a larger excitation field, which can be expressed in terms of the field-dependent Brownian relaxation time. Next, the amplitude of the ac susceptibility became lower for larger excitation fields, and the frequency characteristic of the ac susceptibility moved to a higher frequency compared with that predicted by the Debye theory. Finally, higher harmonics occurred with increasing excitation fields. Approximate equations, that describe such nonlinear behaviors reasonably well, were also obtained. These equations are expected to be useful for developing biosensors based on Brownian relaxation. (C) 2009 The Japan Society of Applied Physics