【作者】 张磊；

【导师】 姜立伟；

【作者基本信息】 吉林大学 ， 理论物理， 2022， 硕士

【摘要】 介观尺度下,对自旋电子学研究而言,界面对器件的性能有着至关重要的影响。作为巨磁阻效应研究的器件模型,自旋阀是一个非磁性的金属间隔层材料隔开两个磁性电极而构成的三明治式的多层结构,因此电极与间隔层材料之间形成两个界面。界面处的原子无序和缺陷会显著破坏自旋阀的磁阻性能,为了尽可能地克服界面处的缺陷对器件性能的影响,我们设计了一种方案来构造自旋阀,即以半金属铁磁性质的Heusler化合物作为电极,根据Slater-Pauling规则,替换其Y-位点上的原子得到相应的非磁间隔层。这样就自然地保证了电极与间隔层之间晶格和能带上的匹配。我们以Co2Fe Al作为电极、Co2Sc Al作为相应的间隔层构造了Co2Fe Al/Co2Sc Al/Co2Fe Al（001）自旋阀。从第一性原理的层面,我们通过形成能和声子谱确认出当Co2Sc Al生长在电极Co2Fe Al的Fe Al-表面时具有最稳定的Fe Al/Co Co-界面。接着将界面处原子的投影态密度与体材料Co2Fe Al相应原子的态密度做对比,我们发现仅有Al原子的自旋向上的态密度在界面处从0.17states/atom/e V下降到0.06 states/atom/e V,界面处继承了体材料的半金属性。因而自旋输运计算展示出了显著地数值为10¹⁰%的巨大磁阻率,这一数值结果要远高于之前文献报道的全Heusler器件的最佳理论值10⁶%。作为一个对比,我们还探索了Fe3Al/Fe2VAl、Mn3Al/Cu3Al两组Heusler化合物分别构成的自旋阀中的磁阻性能,进一步验证了我们器件方案的可行性。基于在磁阻器件中对异质结构界面性质的关注,我们用拓扑非平庸与拓扑平庸材料构建异质结来探索界面磁性的可能。同时在宽带隙半导体Li3Sb[001]和[111]两个晶向上Li（X-位）作为薄膜表面时观察到表面磁性,并且这种表面磁性对外界各种扰动表现出强鲁棒性。更多还原

【Abstract】 On a mesoscopic scale,the interface has a crucial impact on the performance of de-vices for the study of spintronics.As a device model for the study of the Giant magnetore-sistance（GMR）effect,the Spin-Valve（SV）is a sandwich multi-layer structure composed of non-magnetic metal spacer material separating by two magnetic electrodes.Therefore,two interfaces are formed between the electrode and the spacer material.Atomic disorder and defects at the interface will significantly destroy the GMR per-formance of the SV.In order to reduce the disorder at the interface and protect the half metallicity of the electrode at the same region,we propose a scheme to construct a spin valve by replacing the Y-site atoms in the half-metallic Heusler electrode to obtain the corresponding non-magnetic spacer based on the Slater-Pauling rule.In this way,the lat-tice and band match of the two materials can be ensured naturally.By using Co2Fe Al as an electrode and Co2Sc Al as the spacer materials,the Co2Fe Al/Co2Sc Al/Co2Fe Al（001）-SV is constructed.Based on the first-principles calculation,the most stable Fe Al/Co Co-interface is determined both from the phonon spectra and the formation energy when the spacer Co2Sc Al grows on the Fe Al-terminated（001）surface of electrode material Co2Fe Al.By comparing the projected density of states of the interfacial atoms with the corresponding density of states of the bulk electrode material,only the value of the spin-up state of Al changes from 0.17 states/atom/e V to 0.06 states/atom/e V before and after the substitution,the half metallicity at the interface is maintained.As a result,the spin-dependent transport properties show significant theoretical MRop which can reach up to10¹⁰%and is much larger than 10⁶%reported before in“all-Heusler”device.As a com-parison,we further explored the MR properties of SVs composed of two groups of Heusler compounds Fe3Al/Fe2VAl and Mn3Al/Cu3Al respectively,and further verified the feasi-bility of our device scheme.Based on the concern of the interface properties of heterostructures in magnetoresis-tive devices,we constructed heterostructures with topological nontrivial and topological trivial materials to explore the possibility of interface magnetism.At the same time,in the wide-bandgap semiconductor,Li3Sb shows surface magnetism when Li（X-Site）is used as the surface at[001]and[111]crystal orientation,and this surface magnetism shows strong robustness to various external perturbations.更多还原