For spintronics applications, it is highly desirable to realize highly-spin-polarized two-dimensional (2D) electron systems in electrically-controllable epitaxial ultrathin films on semiconductor substrates. Through systematic first-principles investigation, we propose the TcO$_2$ uni-cell layer (one-unit-cell thickness) on rutile TiO$_2$ (001) substrate as a semiconductor heterostructure and use electric field to manipulate its electronic and magnetic properties. Our study shows that the heterostructure is a narrow-gap semiconductor with an antiferromagnet-like ordering when the applied electric field is less than 0.026 V/Å, and then it transits to a half-metallic ferrimagnet with 100\% spin polarization. Our further analysis indicates that the magnetization density and the electronic states near the Fermi level originate mainly from the TcO$_2$ uni-cell layer, with the remaining minor part from the interfacial Ti-O$_2$ monolayers, and the bonds and bond angles quickly converge to the corresponding values of bulk TiO$_2$ when crossing the interface and entering the TiO$_2$ layer. Therefore, the heterostructure is actually a 2D electron system determined by the TcO$_2$ uni-cell layer and the TiO$_2$ substrate. Because the half-metallic phase with 100\% spin polarization can be achieved at 0.026 V/Å, this epitaxial 2D electron system should be usable in spintronics applications.
Spin Seebeck effect in magnetic junctions with a compensated ferrimagnet
Institute for Solid State Physics, The University of Tokyo（东京大学固体物理研究所）；Advanced Science Research Center, Japan Atomic Energy Agency（日本原子能研究开发机构先进科学研究部）；Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences（中国科学院大学喀文利理论科学研究院）；CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences（中国科学院大学中国科学院拓扑量子计算卓越创新中心）；RIKEN Center for Emergent Matter Science (CEMS)（理化学研究所新兴物质科学中心）
Electrical generation and detection of terahertz signal based on spin-wave emission from ferrimagnets
太赫兹（THz）信号主要由光子或电子方法产生，正在寻求用于各种应用，而磁源的开发可能是利用电磁辐射的磁性的必要步骤。我们发现，相对论效应对电流驱动的畴壁运动诱导太赫兹自旋波发射的亚铁磁体。在具有强交换相互作用的材料中，所需的电流密度急剧增加，并迅速超过1012 A m-2，导致器件击穿，因此缺乏实验证据。通过将集体磁化振荡转化为电压信号，我们提出了一种用于太赫兹自旋波电探测的三端器件。通过材料工程，可以获得264 GHz至1.1 THz的宽频率范围和均匀的连续信号，并提高输出功率。作为反向效应，该系统中产生的自旋波能够移动亚铁磁畴壁。我们的工作为THz自旋波的实验验证提供了指导，并对宽带THz自旋电子振荡器以及全磁振子自旋电子器件的设计具有一定的启发意义。
Large spin-wave bullet in a ferrimagnetic insulator driven by spin Hall effect
由于其横向性质，自旋霍尔效应（SHE）提供了激发和检测自旋电流和磁化动力学的可能性，即使在磁性绝缘体中。磁绝缘体具有极低的吉尔伯特阻尼，是研究非线性现象和新型低功率自旋电子学应用的优秀材料。在这里，我们报告的直接成像的电驱动自旋扭矩铁磁共振（ST-FMR）的亚铁磁绝缘体Y $_3$ Fe $_5$ O $_{12}$的激发和检测的基础上的SHE。利用空间分辨微聚焦布里渊光散射（BLS）技术，对Y $_3$ Fe $_5$ O $_{12}$中的自旋动力学进行了直接成像.以前，ST-FMR实验假设整个样品的均匀进动，这在我们的测量中是无效的。一个强大的自旋波本地化的样品的中心，观察表明形成一个非线性的，自本地化的自旋波“子弹”。
Prediction of two-dimensional $π$-electron half-metallic ferrimagnets
International Iberian Nanotechnology Laboratory（伊比利亚纳米技术国际实验室）；Universidade de Santiago de Compostela（圣地亚哥-德孔波斯特拉大学）；Universidad de Alicante（阿利坎特大学）；University of Minho（米尼奥大学）
Strain Tuning of Orbital-Driven Giant Magnetoresistance in van der Waals ferrimagnet Mn$_3$Si$_2$Te$_6$
Institute for Solid State Physics, The University of Tokyo（东京大学固体离子体研究所）；The University of Tokyo（东京大学）；Department of Physics and Astronomy, The University of Manchester（曼彻斯特大学物理与天文学系）；The University of Manchester（曼彻斯特大学）；Department of Physics, Institute of Science Tokyo（东京科学大学物理系）；Institute of Science Tokyo（东京科学大学）
