异质结构磁性薄膜的界面相关性能及其调控与应用研究

发布时间：2018-02-27 09:01

  本文关键词： 磁性多层膜 垂直磁各向异性 隧穿磁电阻 反常霍尔效应 自旋轨道矩　出处：《北京科技大学》2017年博士论文　论文类型：学位论文

【摘要】：具有纳米异质结构的磁性薄膜是自旋电子学的核心应用材料。其中,与维度、尺寸密切相关的表面、界面效应又对材料性能有着至关重要的影响。本论文着眼于分析铁磁金属/氧化物、铁磁/非磁金属等异质界面对薄膜材料磁性能以及自旋相关输运性能的影响;通过实验测量及表征构建界面微结构、界面化学状态与材料性能的关联;利用界面调控进一步优化材料性能;并探索异质结构磁性多层膜的新型自旋逻辑应用。论文主要研究内容及成果如下:(1)成功制备出具有垂直磁各向异性的L10-FePt/MgO/L10-FePt单晶外延隧道结。将界面结构细化至原子终止层尺度,结合理论计算及界面表征研究了 FePt/MgO界面处不同终止层(Fe或Pt)对隧穿磁电阻的影响。(2)通过变温及偏压依赖输运测量研究了 Fe/MgO/Fe/MgO/Fe单晶外延双势垒隧道结中随中间Fe层厚度变化的隧穿行为。利用原子分辨的透射电子显微技术对Fe层形貌及界面结构进行原位表征,构建了动态演变的界面结构与隧穿行为的关联,指出MgO/Fe/MgO界面变化会对输运通道产生调制从而影响体系输运性能。(3)聚焦于铁磁金属/氧化物界面化学状态对材料性能的影响,利用化学稳定的氧化物包覆层以及具有强氧亲和能力的界面金属插层,对无序FePt薄膜、[Pt/Co]3/MgO多层膜以及Ta/CoFeB/MgO/Ta多层膜三种典型材料体系的磁性能及输运性能进行了调控:采用SiO2包覆无序FePt超薄膜使其获得了垂直磁各向异性;在Co/MgO界面处插入优化厚度的Ta,[Pt/Co]3/Ta/MgO经450℃退火后仍然保持热稳定的垂直磁各向异性和较大的反常霍尔输出;将Gd插入CoFeB/MgO界面处,在保持垂直磁各向异性的基础上Ta/CoFeB/Gd/MgO/Ta的有效阻尼因子较之无插层时最多下降70%。(4)基于重金属/铁磁金属/氧化物异质结构中自旋轨道矩引起的磁化翻转特性,在具有垂直磁各向异性的Ta/CoFeB/MgO/Ta多层膜中实验完成了全部16种布尔逻辑运算。更进一步,结合电压调控界面垂直磁各向异性,仿真设计了能够快速运行16种布尔逻辑运算的三端自旋逻辑器件单元。基于该设计思路,实际器件中通过优化材料结构可以实现不依赖磁场的逻辑运算功能。未来集成电路中应用这种新型的自旋逻辑器件,有望融合非易失存储和计算,从而打破当前CMOS工艺以及冯·诺依曼架构体系所面临的发展瓶颈。
[Abstract]:Magnetic thin films with nanoscale heterostructures are the core applications of spin electronics. The interfacial effect has an important effect on the material properties. In this paper, the effects of ferromagnetic metal / oxide, ferromagnetic / non-magnetic metal and other heterogeneous interfaces on the magnetic properties and spin dependent transport properties of thin film materials are analyzed. The interface microstructure was constructed by experimental measurement and characterization, and the relationship between the chemical state of the interface and the properties of the material was obtained, and the properties of the material were further optimized by the interface control. The main contents and results of this thesis are as follows: 1) the epitaxial tunnel junctions of L10-FePt / MgO / L10-FePt single crystal with perpendicular magnetic anisotropy have been successfully fabricated. The interface structure has been refined to the scale of atomic termination layer. Combined with theoretical calculation and interface characterization, the effects of different termination layers (Fe or PT) at FePt/MgO interface on tunneling magnetoresistance were studied. Atomic resolved transmission electron microscopy (TEM) was used to characterize the morphology and interface structure of Fe layer in situ. The relationship between the dynamic evolution of interface structure and tunneling behavior is constructed. It is pointed out that the change of MgO/Fe/MgO interface will modulate the transport channel and thus affect the transport performance of the system. Using chemically stable oxide coating and interfacial metal intercalation with strong oxygen affinity, The magnetic properties and transport properties of disordered FePt films, [Pt/Co] 3 / MgO multilayers and Ta/CoFeB/MgO/Ta multilayers were regulated. The perpendicular magnetic anisotropy was obtained by using SiO2 coating disorder FePt ultrathin films. At the Co/MgO interface, the optimized thickness Ta, [Pt/Co] 3 / Ta / MgO remains thermally stable perpendicular magnetic anisotropy and large anomalous Hall output after annealing at 450 鈩，

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