兰州大学机构库 >物理科学与技术学院
自旋转移矩效应驱动磁性纳米结构的磁化动力学研究
Alternative TitleSpin transfer torque induced magnetization dynamic in magnetic nanostructures
牟从普
Subtype博士
Thesis Advisor王建波
2013-05-29
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name博士
Keyword自旋转移矩 磁性随机存储器 微波辅助 Seebeck效应 微磁学
Abstract巨磁电阻效应已经被广泛的应用在磁性存储器、传感器等领域。近年来发现的自旋转移矩(STT)效应被认为是继GMR效应之后又一里程碑的发现。本论文主要分为微磁学模拟STT效应和实验上研究了横向自旋阀结构中的Seebeck效应两部分。主要结果如下: (1)通过微波磁场辅助的方法,降低了自旋阀和磁性隧道结中磁化反转所需临界电流密度。微波磁场振幅和频率对临界电流密度的减小量影响非常大。微波磁场辅助存在一个最优频率,当微波磁场频率等于最优频率时临界电流密度减小量最大。 (2)我们分别研究了线偏振和圆偏振微波磁场辅助STT激发磁化反转。在圆偏振微波磁场辅助下临界电流密度和磁化反转时间比线偏振微波磁场辅助下的小。 (3)对于In-plane自旋阀结构,其自然共振频率和STT效应激发自由层磁化反转所需临界电流密度随着垂直各向异性常数的增加而减小。而对于Out-plane磁性隧道结而言,临界电流密度以及自然共振频率随着磁晶各向异性常数的增加而增加。 (4)这一部分主要研究了三种横向自旋阀结构中的Seebeck效应。由焦耳热引起的Seebeck电压与注入偏置直流的二次方成正比。但是对于local横向自旋阀结构,Seebeck电压是不对称的,这种不对称来源于异质结构中的Peltier效应。通过基板传输的焦耳热大约是通过铜传输焦耳热的12%。
Other AbstractGiant magnetoresistance (GMR) effect had been extensively used in magnetic memory, magnetic sensor and so on. The spin transfer torque was theoretically predicted by Berger and Slonczewski in 1996, which was considered as milestone after GMR in magnetic. The magnetization can be manipulated by the spin transfer torque rather than the external magnetic field in nanoscale magnetic device. In this thesis, it is investigated that the spin transfer torque induces magnetization switching under microwave magnetic field assisting by micromagnetic simulation, and the Seebeck voltage is systematically investigated in lateral spin valve by two different measurement techniques. The main results of this thesis are as following: (1)The critical current density of magnetization switching induced STT in spin valve and magnetic tunnel junction is systematically investigated under microwave magnetic field assisting by micromagnentic simulation. The simulation results indicate that critical current density and magnetization switching time can be obviously reduced due to the introduction of microwave magnetic field. And the frequency and amplitude of microwave magnetic field can strongly affect both critical current density and magnetization switching time. The minimums of critical current density and magnetization switching time can be obtained, when microwave frequency comes up to the optimal frequency, which is the natural ferromagnetic resonance frequency of spin valve and MTJ. (2) It is investigated that the STT inducing magnetization reversal is assisted by three types microwave magnetic field (circularly polarized, in-plane linearly polarized and out-plane linearly polarized microwave magnetic field). The reducation of critical current density and magnetization switching time under circularly polarized microwave assisted is bigger than that under linearly polarized microwave assisted. (3) Perpendicular anisotropy is very important, because it has an impact not only on dynamic magnetic, but also on STT inducing magnetization reversal. Micromagneitc simulation is carried out to build up a direct relationship between critical current density, natural resonance frequency and uniaxial magnetic anisotropy constant in In-plane spin valve and Out-plane MTJ. In in-plane spin valve, the critical current densiy and natural resonance frequency linearly decrease with the increasing uniaxial magnetic anisotropy constant. But the critical current densiy linearly increases with i...
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Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/228983
Collection物理科学与技术学院
Recommended Citation
GB/T 7714
牟从普. 自旋转移矩效应驱动磁性纳米结构的磁化动力学研究[D]. 兰州. 兰州大学,2013.
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