由于钇铁石榴石(Y₃Fe₅O₁₂，YIG)具有高绝缘性、极低的阻尼因子和长的磁振子衰减长度，近年来在自旋电子学中吸引了人们的极大兴趣，并且大大促进了自旋泵浦、自旋热电子学、自旋波电子学甚至拓扑自旋电子学的研究。钇铁石榴石薄膜和其他稀土铁石榴石薄膜一样，形状各向异性占主导地位，所以通常具有面内易磁化。随着自旋电子学的迅速发展，具有垂直磁各向异性的磁性绝缘体纳米薄膜变得越来越有吸引力。例如，在自旋波电子学中，自旋波传输的构型需要满足磁化方向与传输方向相垂直；利用自旋-轨道力矩可以实现绝缘垂直磁性薄膜磁化方向的翻转，基于这一原理的非易失性磁存储器和逻辑器件，与相应的全金属器件相比，焦耳热将显著减少；由拓扑绝缘体和垂直磁化的绝缘磁性层所构成的异质结构被认为是实现量子反常霍尔效应和其他拓扑磁电效应的有效方法之一。因此，绝缘垂直磁性薄膜及其异质结构成为人们越来越关注的主题。 具有垂直磁各向异性YIG薄膜的制备具有挑战性。文献报道，利用脉冲激光方法在晶格参数大于YIG晶格约1.41％的单晶石榴石衬底上通过特定缓冲层适当减小外延张应力，实现了具有一定垂直磁各向异性的YIG薄膜，复杂的制备过程且较小的垂直磁各向异性都不利于其今后的进一步发展。本论文中，我们选取了三种单晶石榴石衬底，晶格参数均大于YIG的晶格参数，失配度在0.76％到1.58％范围，利用磁控溅射在三种衬底上直接沉积了YIG薄膜，通过后退火处理使制备态的非晶YIG薄膜结晶，获得了垂直磁各向异性可调的高质量(111)YIG外延薄膜。在晶格失配度为1.08％和1.58％的衬底上，由于大应变所导致的磁弹各向异性的绝对优势，薄的YIG薄膜显示出了大的垂直磁各向异性；而应变较小的YIG薄膜，包括应变部分弛豫的较厚YIG薄膜和晶格失配度只有0.76％的YIG薄膜，观察到了明显的磁弹各向异性，但不足以克服形状各向异性因而表现为面内易磁化。进一步，YIG／Pt异质结构的磁输运特性表明，我们制备的垂直磁化和面内磁化YIG外延薄膜均具有高质量的磁表面，可以使自旋流在YIG和Pt的界面进行有效的穿透。上述方法同样适用于其他稀土石榴石磁性薄膜，获得可控的垂直磁各向异性。 在自旋电子学中，纯自旋流的产生和探测一直是人们关注的焦点，非磁金属的自旋霍尔效应及其逆效应被认为是产生和检测纯自旋流的最有效方法之一，而自旋霍尔角则是对材料的电荷流和自旋流相互转换效率的表征。在“铁磁／非磁金属”异质结构中，由于自旋-轨道耦合相关的自旋霍尔效应，通过非磁金属的电流产生自旋流，被铁磁层吸收，对铁磁层磁矩产生力矩作用，是自旋-轨道力矩的最重要来源之一。自旋-轨道力矩可使铁磁层磁矩翻转，相应的临界电流密度与非磁金属的自旋霍尔角紧密相关。寻找大自旋霍尔角材料具有重要意义。 β-W是公认的具有大自旋霍尔角的材料，但是β-W不稳定，经高温退火极易发生相变，转化为稳定的α相，自旋霍尔角大幅减小，因而文献报道的具有垂直磁各向异性、且表现显著自旋.轨道力矩的W／CoFeB／MgO异质结构，其退火温度不能高于300℃，远低于半导体CMOS集成要求的350-400℃。我们发现了一种具有大自旋霍尔角且温度稳定性优于350℃的W-B合金，获得了兼具垂直磁各向异性的W-B／CoFeB／MgO体系；利用直流和脉冲电流诱导的自旋-轨道力矩实现了CoFeB磁化翻转；当外加面内辅助场为130 Oe时，临界翻转电流密度为2×10⁷A／㎝²。我们进一步发现W-B／CoFeB／MgO体系的自旋-轨道力矩由类阻尼有效场主导，W-B的自旋霍尔角为-0.23，与相同厚度的β-W可相比拟。 我们研究了Cu缓冲层对Ir₂₅Mn₇₅自旋霍尔效应的影响。利用自旋塞贝克效应和自旋泵浦对YIG／Ir₂₅Mn₇₅和YIG／Cu／Ir₂₅Mn₇₅异质结构薄膜进行测量，发现Cu层的存在导致Ir₂₅Mn₇₅产生更大的逆自旋霍尔电压。通过磁性表征发现，直接生长在YIG上Ir₂₅Mn₇₅结晶性较差，室温下反铁磁性减弱；而YIG／Cu／Ir₂₅Mn₇₅中的Ir₂₅Mn₇₅则具有较好的结晶性和反铁磁性。利用角分辨X射线光电子能谱技术分析了YIG／Ir₂₅Mn₇₅中Mn的氧化情况，发现Mn以金属相存在，氧化情况不明显。通过铁磁共振测量发现YIG／Cu／Ir₂₅Mn₇₅的界面自旋混合电导略大于YIG／Ir₂₅Mn₇₅。因而Ir₂₅Mn₇₅在YIG／Cu／Ir₂₅Mn₇₅中逆自旋霍尔电压的增大主要来自于缓冲层Cu对Ir₂₅Mn₇₅微结构和相应反铁磁性的影响。 关键词：垂直磁各向异性，自旋霍尔角，自旋-轨道力矩，磁化翻转，缓冲层

 Because of the insulating nature, extremely low Gilbert damping, and large magnon decay length, in recent years, the thin YIG film has attracted significant interest in spintronics, and it greatly facilitates the research on spin pumping, spin caloritronics, magnonics, and even topological spintronics. The YIG films (as well as many other rare-earth iron garnet films) usually favor in-plane spontaneous magnetization due to the overwhelming shape anisotropy. With the rapid progress in spintronics, nanometer-thick insulating magnetic films with perpendicular magnetic anisotropy (PMA) are becoming more appealing. For example, the geometry for spin-wave transport requires the magnetization orthogonal to the propagation direction in magnonics; nonvolatile magnetic memories and logic devices based on insulating perpendicular magnetic films switched by spin-orbit torque (SOT) will significantly reduce heat dissipation in comparison with the all-metallic counterpart; heterostructures consisting of a topological insulator and an insulating magnetic layer with PMA are regarded as a promising approach to realize the quantum anomalous Hall effect and other topological magnetoelectric effects. Therefore, insulating perpendicular magnetic thin films and their heterostructures have been the subject of increasing interest. The development of YIG films with large PMA seems to be more challenging. It has been reported that YIG thin films with PMA have been successfully prepared on a single crystal garnet substrate with lattice constants exceeding that of YIG by a ratio 1.41% via a specific buffer layer by pulsed laser deposition, and the complex preparation process and a rather gentle PMA are not favor for its further development. In this paper, high quality epitaxial (111) YIG films with the tunable PMA are fabricated by annealing amorphous precursor films that are sputtering deposited on three kinds of single crystal garnet substrates with lattice constants exceeding that of YIG by a ratio from 0.76% to 1.58%. Large PMA is demonstrated in the fully strained thin YIG films on substrates with lattice mismatch from 1.05% to 1.58% due to the overwhelming of the magnetoelastic anisotropy. Less-strained YIG films, corresponding to partial strain relaxation at larger YIG thickness or smaller substrate lattice mismatch at 0.76%, show substantial but insufficient magnetoelastic anisotropy to overcome shape anisotropy. Magnetotransport characterization on YIG/Pt bilayers shows the high quality YIG surface with efficient spin current transmission across the heterostructure interface. The present method should also be applicable to the epitaxial growth of other rare earth iron garnet thin films with unprecedented ability to acquire and control PMA. In spintronics, the generation and detection of spin currents have always been the focus of attention. The spin Hall effect and its inverse effect in metal and alloys are regarded as a promising way to generated and detect pure spin currents. The spin Hall angle represents the efficiency of the conversion between charge current and spin current. In the ferromagnetic metal/non-magnetic metal heterostructure, due to the spin Hall effect associated with spin-orbit coupling, the spin current generated by the current in non-magnetic metal is absorbed by the ferromagnet layer, and exerts a torque effect on the ferromagnetic layer. This is one of the most import sources of the spin-orbit torque. The spin-orbit torque can switch the magnetization of ferromagnetic materials and the corresponding critical current density is closely related to the spin Hall angle of non-magnetic metals. It is of great significance to find materials with large spin Hall angle. β-W is well-known for its a large spin Hall angle, but it is unstable. After high temperature annealing, phase transition is easy to occur, β-W is transformed into stable a phase, and the spin Hall angle decreases greatly. Therefore, it has been reported that the W/CoFeB/MgO heterostructures with PMA and significant spin-orbit torque can not be annealed above 300 ℃, which is much lower than 350-400 ℃ required for semiconductor CMOS integration. A W-B alloy with large spin Hall angle and temperature stability better than 350 ℃ was prepared, and the W-B/CoFeB/MgO heterostructures with PMA was obtained. The magnetization switching of CoFeB is realized by the spin-orbit torque induced by DC and pulse current. When in-plane external field is 130 Oe, the critical current density is 2×10⁷A/㎝². We further find the spin-orbit torque of W-B/CoFeB/MgO is dominated by the damping-like effective field, and the spin Hall angle of W-B is -0.23, which is comparable to that of β-W with the same thickness. The effect of Cu buffer layer on the spin Hall effect of In₂₅Mn₇₅ is invesgated in this paper. The spin Seebeck effect and spin pumping technique are used to measure YIG/Ir₂₅Mn₇₅ and YIG/Cu/In₂₅Mn₇₅ heterostructure films, we found that the presence of Cu layer resulted in a larger inverse spin Hall voltage of In₂₅Mn₇₅. The results of magnetic characterization show that the crystallinity of In₂₅Mn₇₅ grown on YIG is poor and the antiferromagnetism decreases at room temperature, while In₂₅Mn₇₅ in YIG/Cu/Ir₂₅Mn₇₅ has better crystallinity and antiferromagnetism. The oxidation of Mn in was tested by angular resolved X-ray photoelectron spectroscopy. The results show that Mn exists in metallic phase and the oxidation is not obvious. The interfacial spin mixing conductance ofYIG/Cu/In₂₅Mn₇₅ is slightly larger than that of YIG/In₂₅Mn₇₅ by ferromagnetic resonance measurements. Therefore, the increase of inverse spin Hall voltage of Ir₂₅Mn₇₅ in YIG/Cu/In₂₅Mn₇₅ is mainly due to the effect of buffer layer Cu on the microstructure and corresponding antiferromagnetism of In₂₅Mn₇₅. Key Words; Perpendicular magnetic anisotropy, Spin Hall angle, Spin-orbit torque, Magnetization switching, Buffer layer