磁性薄膜的反常霍尔效应和磁性研究

发布时间：2018-10-09 07:33

【摘要】：纳米铁磁金属薄膜,近年来不再限于宏观的、静态的物质磁性,而是随着研究的不断深入,研究方向逐渐拓展到运动的、单电子的自旋变化。于是实验上自旋霍尔效应、反常霍尔效应、隧道磁阻(Tunneling Magnetoresistance,TMR)和庞磁阻效应(Colossal magnetoresistance,CMR)、自旋量子霍尔效应等一系列新的现象应运而生,并由此拓展产生一个结合磁学与微电子学的研究领域:自旋电子学。反常霍尔效应(anomalous Hall effect,AHE)是自旋电子学研究课题中的热点之一。因为霍尔于1889年就已经发现了反常霍尔效应,但是关于其机理有两种说法,一是来自于非本征机制,另一种是本征机制。至今两种机制的争论还在继续。因此对其进行研究显得尤为重要。本文以Fe-N系化合物薄膜、CoCrPt薄膜为研究对象,对其微结构、磁性、输运特性特别是反常霍尔效应进行了系统研究。主要工作和研究成果如下:(1)在室温下采用射频磁控溅射方法制备氮化铁薄膜,研究了不同氮含量条件下薄膜的导电机制。实验结果表明:随着氮含量的增加,观察到薄膜的导电机制从金属过渡到半导体。(2)霍尔电阻的测量表明所有氮化铁薄膜样品在高电阻区域反常霍尔电阻率与纵向电阻率的标度关系为线性,即反常霍尔效应遵循斜散射机制,但相应的反常霍尔电导率与纵向电导率的关系不总是呈线性。(3)采用磁控溅射方法制备CoCrPt薄膜并系统研究了衬底层Cu层厚度对薄膜结构、磁性、反常霍尔效应的影响,结果表明所有样品具有良好的垂直磁性(PMA)。随着Cu层厚度的增加,矫顽力cH变小,颗粒之间的相互作用变强。矫顽力cH的变化是由颗粒之间的交互作用引起的。薄膜样品的标度指数从n=1.46变到n=1,这表明反常霍尔效应机制由斜散射和边跳机制的共同作用转变为单纯的斜散射,同时也表明Cu层厚度较薄的样品无序度较高。此趋势与样品中的弱局域化效应一致。
[Abstract]:In recent years, the ferromagnetic nanometallic thin films are no longer confined to the macroscopic and static magnetic properties, but with the development of the research, the research direction is gradually extended to the spin variation of the moving, single electron. A series of new phenomena, such as spin Hall effect, anomalous Hall effect, tunneling magnetoresistive effect (Tunneling Magnetoresistance,TMR), colossal magnetoresistive effect (Colossal magnetoresistance,CMR) and spin quantum Hall effect come into being. A new research field combining magnetics and microelectronics has been developed: spin electronics. Anomalous Hall effect (anomalous Hall effect,AHE) is one of the hot topics in spin electronics. Hall discovered the anomalous Hall effect in 1889, but there are two theories about its mechanism, one is from the extrinsic mechanism, the other is the intrinsic mechanism. The debate over the two mechanisms continues to this day. Therefore, it is particularly important to study it. In this paper, the microstructures, magnetic properties, transport properties, especially anomalous Hall effect of Fe-N compound thin films are studied. The main results are as follows: (1) the electroconductive mechanism of Fe _ 3N _ 4 thin films prepared by RF magnetron sputtering at room temperature was studied. The results show that: with the increase of nitrogen content, It has been observed that the conductive mechanism of the film is transitioning from metal to semiconductor. (2) the measurement of Hall resistance shows that the scale relationship between anomalous Hall resistivity and longitudinal resistivity of all samples of iron nitride films in high resistance region is linear. The anomalous Hall effect follows the oblique scattering mechanism, but the relationship between the anomalous Hall conductivity and the longitudinal conductivity is not always linear. (3) CoCrPt thin films are prepared by magnetron sputtering and the effects of the thickness of the Cu layer on the structure and magnetic properties of the films are systematically studied. The effect of anomalous Hall effect shows that all samples have good perpendicular magnetic (PMA). With the increase of the thickness of Cu layer, the coercivity cH becomes smaller and the interaction between particles becomes stronger. The change of coercivity cH is caused by the interaction between particles. The scale exponent of the thin film samples changed from nb1.46 to nb-1, which indicates that the anomalous Hall effect mechanism changed from oblique scattering and edge-hop mechanism to simple oblique scattering. It also shows that the disordered degree of the thin Cu layer is higher than that of the sample with thin thickness. This trend is consistent with the weak localization effect in the sample.
【学位授予单位】：南京邮电大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM27;TB383.2

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