【作者】 杨艳敏；

【导师】 黄志高；

【作者基本信息】 福建师范大学 ， 理论物理， 2005， 硕士

【摘要】 本文采用数值计算的方法研究了纳米磁性材料的磁光科尔效应和磁电阻效应。主要内容安排如下: 1.首先介绍磁光效应的基本知识和测量装置图,特别介绍了磁光科尔效应的三种机制和相应的测量配置。然后介绍了磁电阻效应的一些基本知识和研究背景,主要介绍了颗粒膜的巨磁电阻效应。在第二章中重点介绍了4×4矩阵法和蒙特卡罗方法。 2.其次,利用4×4矩阵法和界面等效层理论,引入界面效应,模拟了(TbFeCo)100-xPrx磁性多层膜系统的磁光特性随入射角和磁性层厚度的变化以及混合界面层界面结构变化的关系,发现界面结构对结果有重要的影响。 3.重点利用4×4矩阵法结合蒙特卡罗方法模拟颗粒膜的磁光科尔磁滞回线和磁电阻效应,模拟的磁光效应磁滞回线和巨磁电阻曲线与实验结果吻合的很好。 首先,理论模拟VSM和MOKE效应测得的NixSiO2(1-x)颗粒膜的磁滞同线。结果表明,一般在倾斜入射的情况下,用磁光科尔效应测得的磁滞回线和用VSM测得的磁滞回线是有区别的,这种差别随着入射角的增大而增大:对于富Ni颗粒的强铁磁性的薄膜,这种差别比弱磁性和复合磁性薄膜的要小。 其次,计算了CoxAg(1-x)颗粒膜的磁光科尔效应和巨磁电阻效应。模拟结果表明,和向异性作用和偶极相互作用对磁光科尔效应和巨磁电阻效应有显著的影响;同时计算了CoxAg(1-x)颗粒膜的Kt,Lt在解释磁性颗粒膜的巨磁电阻效应有很大的帮助。Kt是一个与零场电阻ρ0和散射系数κ有关的参数,Kt=κ/ρ0。 4.最后,基于蒙特卡罗模拟和网格电阻模型,研究了二维各向异性纳米颗粒点阵的隧道磁电阻效应。模拟结果表明,考虑交换相互作用以后,当偶极相互作用较弱时,磁电阻峰值随着偶极相互作用的增强而减小:当偶极相互作用较强时,磁电阻峰值随着偶极相互作用的增强而增大。模拟结果能够利用不同能量(无规各向异性能,偶极相互作用能和交换相互作用能)之间的竞争作用来解释。更多还原

【Abstract】 In this thesis the Kerr effect and magnetoresistance of nanomagnetic materials have been studied with numerical methods.The main contents of this paper are arranged asfollows:Firstly, we briefly present the knowledge of the magneto-optical effect and its experimental scheme, especially three mechanisms of the magneto-optical Kerr effects. Subsequently, we also expound the basical ideas of the magnetoresistance, especially for giant magnetoresistance of the granular films. Additionally, we describe the 4×4 matrix method and Monte Carlo simulation technique in the second chapter.Secondly, with the 4×4 matrix method and the theory of the equivalent layer, the Kerr effects for （TbFeCo）_100-xPr_x magnetic multilayered-films, as a function of interfacial layer, the thickness of magnetic layer and the incident angle, have been simulated. It is found that the structure of interface played an important role for magneto-optical effects in magnetic multilayered filmThirdly, based on the Monte Carlo and 4×4 matrix method, we present the theoretical calculation of the Kerr loops and giant magnetoresistance curves in granular films.The calculated results of both Kerr loops and GMR curves are in good agreement with experimental ones.On one hand, the experimental hysteresis loops for Ni_xSiO_2（1-X） granular films are calculated. The simulated results reveal that: generally, the difference between the hysteresis loops measured from VSM and Kerr effect respectively always exists for certain incident angle; the difference increases with increasing incident angle; it is smaller in strong ferromagnetic films than that in weak or mixed magnetic films.On the other hand, the Kerr loops and giant magnetoresistace curves in Co_xAg_1-X granular films are calculated. The simulated results reveal that: the anisotropy energy and the dipolar interaction influence evidently the Kerr loops and the giant magnetoresistace effect; the value of K₁ for the Co_xAg_1-x granular films are calculated, which plays animportant role for explaining the giant magnetoresistace effect of the granular films. It should be pointed out that the constant K, is related with the resistivity at a zero field and the scattering parameter constant.Fourly, based on Monte Carlo simulations and resistor network model, the tunneling magnetoresistance （TMR） for the square anisotropic magnetic nanoparticle arrays has been studied. The simulated results reveal that: with the exchange coupling J, for small dipolar interaction, the value of TMRniix decreases with increasing value of D, while it increases with increasing value of D for large dipolar interaction. Those behaviors can be explained with the competition of the different energies, including the random anisotropy, exchange and dipolar energies.更多还原