【作者】 钟克华；

【导师】 黄志高；

【作者基本信息】 福建师范大学 ， 理论物理， 2006， 硕士

【摘要】 本论文采用数值计算的方法研究了磁性纳米线及其阵列的磁特性，目的是通过探究纳米线及其阵列的宏观磁物理量，进而探究其微观磁化行为。论文的内容具体安排如下： 1、首先介绍纳米材料的基本概念、发展史和物理性质，磁性纳米线阵列的发展史及研究现状。接着主要介绍了本论文所涉及到的基本理论基础包括磁性材料的磁滞现象、数值计算中的基本能量项以及纳米线磁化反转模式。然后重点介绍了蒙特卡罗方法和快速傅立叶变换微磁学方法。 2、其次，采用蒙特卡罗方法具体研究了铁、钴纳米线在反磁化过程中的磁滞回线、矫顽力随温度或角度的变化关系、开关场随角度的关系等宏观磁性质及磁化反转机制，模拟结果与实验结果吻合得较好。 首先我们分别采用两种最小划分单元（球形和立方形）对铁纳米线进行研究，结果表明：①与实验结果相比较，球形划分单元比立方形划分单元所得到的结果更加准确；②磁性纳米线的矫顽力随线直径的增大而减小，这个趋势与实验结果一致；③矫顽力随温度的变化关系可以用T^-α律很好地描述。 其次，我们模拟计算了室温下，单根钴纳米线的磁滞回线，模拟得到的开关场随角度的变化关系与实验结果吻合得较好。同时，我们还探究了矫顽力与角度的关系，结果表明：①矫顽力随角度的变化关系依赖于纳米线的直径；②矫顽力、开关场与角度的关系明显不同于球链模型中经典的一致转动模式所得到的结果；③磁化反转组态显示了直径较小的纳米线的磁化反转以成核传播形式为主，而直径较大的纳米线的磁化反转过程以涡旋传播形式为主。 3、然后，我们提出一个新模型研究钴纳米线阵列中线间的静磁相互作用对阵列的磁性质的影响，模拟结果较好地解释了实验数据，发现钴纳米线阵列线间相互作用和磁晶各向异性对阵列的宏观磁性质产生了很大的影响。 4、最后，在前面的模拟计算中，我们发现程序的计算时间主要花在偶极相互作用能项的计算，为了减少计算时间，提高计算效率，我们在前人的基础上发展了一种快速计算偶极相互作用的方法——快速傅立叶变换微磁学方法，结果表明该方法是一种能快速有效地计算包含远距离偶极相互作用的磁性系统的磁特性的方法。更多还原

【Abstract】 In this thesis, the magnetic properties of nanowires and their arraies have been studied with numerical methods. The purpose is to investigate the magnetization reversal of nanowires by studying the macroscopical quantity. The main contents of this paper are arranged as follows:Firstly, we present the essential conception, phylogeny, physical characters of nanomaterial, the phylogeny and research actuality of magnetic nanowire array. Following, we mostly present the basal theory involved in this paper. It included magnetic hysteresis loops, the energy terms considered in the simulation and the magnetic reversal mechanism. Afterward, we chiefly introduce Monte Carlo method and fast Fourier transformation and micromagnetism （FFTM）.Secondly, based on Monte Carlo method, we investigated magnetic hysteresis loops, coercivity as functions of temperature and angle, switching field as a function of angle, and the magnetic reversal mechanism. The simulated results are consistent with the experimental data.On one hand, using two kinds of discretization cells regular global-shaped and regular cubic-shaped as minimum element, the magnetic properties of Fe nanowire were studied. The simulation results reveal as follows:①The simulated results using the global-shaped discretization cell have more accurate results which is compared to the experimental result than those using the cubic-shaped discretization cell does.②The coercivity of the magnetic nanowire decreases with increasing nanowire diameter. This change trend is agreement with the experimental fact.③The T^-α power-law describes the H_C-T curves well.On the other hand, based on Monte Carlo method, we simulate the magnetization curves of various single Co nanowires at room temperature. The simulated switching field as a function of angles （θ） between the field and wire axis fits well with the experimental data. Correspondingly, the coercivity as a function of angles is presented. The simulated results indicate that （1） the coercivity as a function of angles is found to depend on the更多还原