【作者】 王日兴；

【导师】 贺鹏斌； 王岩国；

【作者基本信息】 湖南大学 ， 凝聚态物理， 2009， 硕士

【摘要】 近年来,自旋电子学由于其丰富的物理内涵和广泛的器件应用前景己成为凝聚态物理研究的热点领域。GMR和TMR等效应提出以来,便在读写磁头、磁存储元件、磁场探测器,微波激发等领域得到了广泛应用。特别是1996年“自旋转移矩”效应的理论预言和后面的实验证实,打破了传统的采用磁场来改变或翻转薄膜材料磁矩方向的方法,开创性地采用自旋极化电流直接实现磁矩反转或激发自旋波。本论文主要对倾斜各向异性磁性多层膜中的铁磁共振进行了理论研究。首先,我们简单地介绍了铁磁材料中的相互作用能以及朗道-栗弗席兹-吉尔伯特(LLG)动力学方程。然后我们在只考虑各向异性能和退磁能的情形下,利用线性展开包含自旋转移矩的LLG动力学方程的方法,获得了电流和频率调节的铁磁共振谱,并且分析了平衡位置,共振位置和共振线宽随直流电流密度和钉扎层磁矩方向的变化关系,讨论了电流密度以及钉扎层磁矩方向对功率密度的影响。研究表明：通过选择合适的电流密度和钉扎层磁矩方向,可以从电流泵浦最大的能量到自由层。这一点对提高电流驱动的微波振荡器以及电流感应磁矩翻转的效率是非常有用的。最后,我们考虑了外磁场,用类似的线性方法研究了射频磁场激发的铁磁共振谱。研究表明：当钉扎层为倾斜各向异性时,共振磁场,共振线宽,进动频率以及自由层磁矩的平衡位置都可以通过改变直流电流密度的大小来调节。除了改变电流的大小和方向以为,我们还可以通过改变钉扎层的磁矩方向来改变磁系统中的能量吸收和发散。更多还原

【Abstract】 Recently, spintronics has become a hot research field in condensed matter physics due to its abundant physical connotation and widely device application prospect. Since giant magnetoresistive(GMR) and tunneling magnetoresistive(TMR) effect are put forward, they have been widely applied in read-write heads, magnetic storage devices, magnetic detectors and microwave excitation etc. Especially, as the result of theoretical predictions in 1996 and later experimental verification of spin-transfer torque, it breaks the traditional method driven by the magnetic field to change or switch the magnetization direction of thin film materials. This new physical mechanism initially realizes the magnetization reversal or excites spin wave by using the spin-polarized current. In this thesis, we mainly investigate the ferromagnetic resonance in magnetic trilayers with a tilted spin polarizer theoretically.First of all, we simply introduce the interaction energy and Landau-Lifshitz-Gilbert (LLG) magnetic dynamics equation. Then, under consideration of anisotropic energy and demagnetization energy, we spread the LLG equation including the spin torque term by the linearization method and obtain the current-and frequency-swept resonant spectra. At the same time, we analysis the dependences of the equilibrium position, resonant location and resonant linewidth on the current and the direction of the pinned magnetization. The influence of the dc current and the pinned magnetization on the power density is also discussed. The research shows that we can acquire the most energy pumping from the current to the free layer by optimizing the current density and the direction of the pinned magnetization in some regions. This is useful for improving the efficiency of current-driven microwave oscillation and current-induced magnetization reversal. Finally, we consider the static magnetic field and present a theoretical investigation of ferromagnetic resonance excited by rf magnetic field in magnetic trilayers with tilted anisotropy by the similar method. We find that the resonant magnetic field, the resonant linewidth, the precessional frequency, and the axis of the magnetization in the free layer are all changed by the spin-polarized current in the present of tilted pinned magnetization. Except for the direction and magnitude of spin polarized current, turning the direction of pinned magnetization provides a new choice of adjusting the pumping and dissipation of energy in the magnetic system.更多还原