垂直磁化膜中的反常霍尔效应及磁性斯格明子研究

发布时间：2018-04-04 18:35

本文选题：CoFeB垂直磁化膜　切入点：反常霍尔效应　出处：《华中科技大学》2015年硕士论文

【摘要】：近年来,具有垂直磁各向异性的磁性纳米结构由于其优秀的特性和广泛的应用领域,逐渐成为国内外研究小组的研究热点。例如,近期有研究小组报道,在MgO/CoFeB/Ta垂直磁化膜中发现了巨大的线性反常霍尔电阻;此外,新型的磁性斯格明子磁存储器件也需要用到垂直磁化薄膜,例如,近期有研究小组在具有垂直磁各向异性的[Co/Pt]N多层膜中发现了室温下稳定的磁性斯格明子。虽然垂直磁性纳米结构已经有很多研究,但是还有一些存在的问题没有阐述清楚。例如,虽然在MgO/CoFeB/Ta垂直磁化膜中发现了巨大的线性反常霍尔电阻,但是基于垂直磁化膜反常霍尔效应的高灵敏度磁传感器在低温下工作的情况目前还很少有研究;另外,尽管学术界认为基于磁性斯格明子的垂直磁性纳米线是非常有应用前景的新型磁存储单元,但是对于电流和自旋波驱动磁性斯格明子在垂直磁性纳米线中的动态过程目前还需要进一步研究。本文以具有垂直磁各向异性的纳米薄膜和纳米线为研究对象,实验上通过高真空磁控溅射系统制备薄膜,深入研究了弱局域化作用对MgO/CoFeB/Ta垂直磁化膜反常霍尔效应的影响;同时,本文还通过微磁学模拟的方法,研究了电流以及自旋波驱动磁性斯格明子在垂直磁性纳米线中的动态过程。实验上,我们通过磁控溅射制备了厚度在1.7 nm~10.5 nm范围内的具有面内磁各向异性的CoFeB非晶薄膜,以及CoFeB厚度在0.8 nm~1.4 nm之间具有垂直磁各向异性的MgO/CoFeB/Ta薄膜。继而,我们测量了非晶态CoFeB单层膜以及MgO/CoFeB/Ta垂直磁化膜的低温电子输运特性。实验发现,对于非晶态CoFeB单层薄膜,当薄膜厚度大于3 nm时,边界跳跃机制是反常霍尔效应的主导机制,弱局域化作用对反常霍尔效应的影响实验观察不到,当薄膜厚度小于3 nm时,反常霍尔效应由边界跳跃机制和斜散射机制共同产生,并且弱局域化作用对反常霍尔效应的影响可以实验观察到;对于MgO/CoFeB/Ta垂直磁化膜,由于Ta膜层为电子提供了一个额外的输运通道,弱局域化作用在薄膜的方块电阻R0大于1.5 k?时才能观察到。此外,我们通过微磁学模拟的方法研究了磁性斯格明子在垂直磁性纳米线中移动的动态过程。研究发现,磁性斯格明子的尺寸取决于垂直磁性纳米线的本征磁学参数以及外加磁场的大小,而且,电流驱动磁性斯格明子移动的速度与磁性斯格明子的尺寸成正比。其次,磁性斯格明子通过垂直磁性纳米线缺陷的阈值电流密度不仅与缺陷的大小有关,还与斯格明子-斯格明子之间的相互作用密切相关。另外,自旋波也可以驱动磁性斯格明子在垂直磁性纳米线中移动,其移动速度与自旋波的频率、自旋波激发场大小、以及斯格明子的尺寸密切相关。
[Abstract]:In recent years, magnetic nanostructures with perpendicular magnetic anisotropy have gradually become the research focus of domestic and foreign research groups because of their excellent properties and wide application fields.For example, a recent team has reported that large linear anomalous Hall resistors have been found in MgO/CoFeB/Ta vertical magnetization films; in addition, new magnetic Schumminon magnetic memory devices need to use perpendicular magnetized films, such as,Recently, a team of researchers found a stable magnetic Schumminon at room temperature in [Co/Pt] N multilayers with perpendicular magnetic anisotropy.Although there have been many studies on perpendicular magnetic nanostructures, there are still some existing problems that have not been clarified.For example, although large linear anomalous Hall resistors have been found in MgO/CoFeB/Ta perpendicular magnetized films, very little research has been done on high sensitivity magnetic sensors based on perpendicular magnetic film anomalous Hall effect at low temperatures.Although the academic community considers magnetic magnetic nanowires based on magnetic Sgrimings to be a promising new magnetic memory cell,However, the dynamic process of magnetic Schumminon driven by current and spin wave in vertical magnetic nanowires needs further study.In this paper, the perpendicular magnetic anisotropy nanocrystalline films and nanowires are studied. The effect of weak localization on the anomalous Hall effect of MgO/CoFeB/Ta perpendicular magnetized films is studied experimentally by a high vacuum magnetron sputtering system.The dynamic processes of current and spin-wave driven magnetic Schumminon in vertical magnetic nanowires are also studied by means of micromagnetics simulation.Experimentally, CoFeB amorphous films with in-plane magnetic anisotropy and CoFeB films with vertical magnetic anisotropy between 0.8 nm~1.4 nm with thickness of 1.7 nm~10.5 nm were prepared by magnetron sputtering.Then we measured the electron transport characteristics of amorphous CoFeB monolayer and MgO/CoFeB/Ta vertical magnetized film at low temperature.It is found that when the thickness of amorphous CoFeB monolayer films is more than 3 nm, the boundary jump mechanism is the dominant mechanism of the anomalous Hall effect, but the effect of weak localization on the anomalous Hall effect is not observed experimentally.When the film thickness is less than 3 nm, the anomalous Hall effect is produced by the boundary jump mechanism and the oblique scattering mechanism, and the effect of weak localization on the anomalous Hall effect can be observed experimentally.Because the Ta film provides an additional transport channel for electrons, weak localization occurs when the sheet resistance R0 of the film is greater than 1.5 k?It is only when you observe it that you can see it.In addition, we study the dynamic process of magnetic Sgrimminon moving in vertical magnetic nanowires by means of micromagnetics simulation.It is found that the size of the magnetic Schumminon depends on the intrinsic magnetic parameters of the vertical magnetic nanowires and the magnitude of the applied magnetic field. Moreover, the speed of the magnetic Schumminon moving by the current drive is proportional to the size of the magnetic Schumminon.Secondly, the threshold current density of magnetic Sgrimminon through vertical magnetic nanowire defects is related not only to the size of defects, but also to the interaction between Sgrimings and Signitons.In addition, the spin-wave can also drive the magnetic Schumminon to move in the vertical magnetic nanowires. Its moving speed is closely related to the frequency of the spin-wave, the magnitude of the spin-wave excitation field, and the size of the spin-minitron.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1

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