The spin filtering effect, distinct decaying lengths experienced by oppositely spin-polarized electrons in a magnetic barrier, generally occurs in ferromagnetic (FM) insulators or semiconductors. With the rise of altermagnetic (ALM) materials which exhibit similar capability of spin-polarizing electrons with ferromagnets, it is a nature question whether the ALM insulators or semiconductors can also act as unique barriers for the spin splitting effect. Here, through first-principles calculations, we investigated the complex band structure of the ALM insulator FeF$_2$ and found that it possesses an anisotropic spin filtering effect: along the [001] direction of FeF$_2$, a current remains spin-neutral but has locally nonvanishing spin polarizations in the momentum space; moreover, along the [110] direction of FeF$_2$, a current will be globally spin-polarized by different attenuation lengths of oppositely spin-polarized electrons. Leveraging this anisotropic spin filtering effect, we designed two types of MTJs with the ALM barrier: ALM electrode/ALM insulator barrier/non-magnetic (NM) electrode and FM electrode/ALM insulator barrier/NM electrode, using RuO$_2$(001)/FeF$_2$/IrO$_2$ and CrO$_2$(110)/FeF$_2$/IrO$_2$ as the corresponding prototypes, respectively. We found that these two proposed MTJs exhibited the tunneling magnetoresistance (TMR) ratios of 216\% and 3956\%, by matching the conduction channels of the electrodes and the spin-resolved lowest decay rate of the barrier in the momentum space. Our work deepens and generalizes understanding toward the spin filtering effect for the rising ALM insulators and semiconductors, and broadens applications of the AFM spintronics.
All-Altermagnetic Tunnel Junction of RuO2/NiF2/RuO2
Huazhong University of Science and Technology（华中科技大学）；Florida State University（佛罗里达州立大学）；National High Magnetic Field Laboratory（国家强磁场实验室）；Columbia University（哥伦比亚大学）
Layer-dependent quantum transport in KV2Se2O-based altermagnetic tunnel junctions
School of Microelectronics, Nanjing University of Science and Technology（南京理工大学微电子学院）；Jiangsu Provincial Engineering Research Center of Low Dimensional Physics and New Energy, and School of Science, Nanjing University of Posts and Telecommunications（南京邮电大学低维物理与新能源江苏省重点实验室及理学院）
Above room temperature multiferroic tunnel junction with the altermagnetic metal CrSb
Huazhong University of Science and Technology（华中科技大学）；Florida State University（佛罗里达州立大学）；National High Magnetic Field Laboratory（国家强磁场实验室）；Charles University（查理大学）
Surface Functionalization Enables Two-Dimensional Altermagnetism and Giant Tunnel Magnetoresistance
Eastern Institute of Technology（东方理工大学）；Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences（中国科学院宁波材料技术与工程研究所）；Fuzhou University（福州大学）
Room temperature spin filtering in epitaxial cobalt-ferrite tunnel barriers
我们报告的直接实验证据，室温自旋过滤的磁性隧道结（MTJ）含有CoFe 2 O 4隧道势垒通过隧道磁阻（TMR）测量。Pt（111）/CoFe_2 O_4（111）/γ-Al_2 O_3（111）/Co（0001）全外延MTJ的生长是为了获得能够在室温下工作的高质量系统。自旋极化输运测量显示，在2K和290 K下，TMR值分别为-18%和-3%。此外，TMR比遵循一个独特的偏置电压依赖性，这在理论上已经被预测为在MTJ中包含磁势垒的自旋过滤的签名。因此，CoFe 2 O 4隧道势垒提供了一个模型系统，以调查在很宽的温度范围内的自旋过滤。
Altermagnetic spin textures: Emergent electrodynamics, quantum geometry, and probes
Hearne Institute of Theoretical Physics, Department of Physics & Astronomy, Louisiana State University（路易斯安那州立大学物理与天文学系希恩理论物理研究所）；Institute for Theoretical Physics III, University of Stuttgart（斯图加特大学理论物理第三研究所）
Dirac edge states as signature of two-dimensional altermagnetic topological crystalline phase
Universitá degli Studi di Milano（米兰大学）；Institute of Physics, Polish Academy of Sciences（波兰科学院物理研究所）；International Research Centre Magtop, Institute of Physics, Polish Academy of Sciences（波兰科学院物理研究所磁顶国际研究中心）；SPIN-CNR, UOS Salerno（萨莱诺统一办公室自旋-意大利国家研究委员会）；Consiglio Nazionale delle Ricerche (CNR-SPIN)（意大利国家研究委员会（CNR-SPIN））
All-electrically controlled spintronics in altermagnetic heterostructures
School of Science, Sun Yat-sen University（中山大学科学学院）；School of Physics and Materials Science, Guangzhou University（广州大学物理与材料科学学院）；School of Humanities and Basic Sciences, Shenzhen Institute of Information Technology（深圳信息职业技术学院人文基础学院）；Institute of Materials, Ningbo University of Technology（宁波工程学院材料研究所）；Department of Physics and Astronomy, Uppsala University（乌普萨拉大学物理与天文学系）
Controlling an altermagnetic spin density wave in the kagome magnet CsCr3Sb5
Nanyang Technological University（南洋理工大学）；Hangzhou Normal University（杭州师范大学）；Zhejiang University（浙江大学）；Zhejiang University of Technology（浙江工业大学）；Chinese Academy of Sciences（中国科学院）
Max Planck Institute for the Physics of Complex Systems（马克斯·普朗克复杂系统物理研究所）；Institute of Physics, Czech Academy of Sciences（捷克科学院物理研究所）；Max Planck Institute for Chemical Physics of Solids（马克斯·普朗克固体化学物理研究所）
Oxide layer boron leads to reduced symmetry spin filtering magnetic tunnel junctions
对FeCoB/MgO/FeCoB隧道结的实验研究表明，硼在溅射过程中扩散到MgO中，形成多晶Mg-B-O区。这些隧道结提供高隧穿磁阻值和低RA产物。然而，Mg-B-O区域的晶体结构仍然未知。使用密度泛函技术，我研究了三种潜在的镁（B）氧化物，包括Mg $_{2}$ B $_{2}$ O $_{5}$（单斜晶系和三斜晶系）和斜方晶系矿物Kotoite（Mg $_3$ B $_2$ O $_6$）。Kotoite是形成磁性隧道结的最佳候选者。Kotoite的（100）面与（001）MgO具有良好的晶格匹配，并且在退火过程中可以将相邻的FeCo模板化为bcc层。Kotoite的复杂能带结构分析表明，C $_{2v}$ $\tildeΔ_1$带具有比C $_{2v}$ $\tildeΔ_4$带小得多的虚k分量。基于对称性分析，FeCo中的多数自旋$Δ_1$带应与Kotoite $\tildeΔ_1$带良好耦合，而少数FeCo $Δ_5$将与$\tildeΔ_4$带部分耦合。Kotoite提供了一种新的途径，高隧穿磁电阻的基础上自旋过滤的低对称性的氧化物区域。
Spin filtering effect in intrinsic 2D magnetic semiconductor Cr2Ge2Te6
采用机械剥离法和叠层法制备了Fe_3GeTe_2/Cr_2Ge_2Te_6/石墨的vanderWaals（vdW）磁性异质结，并对其磁输运特性进行了详细的研究。在低偏置电压下，已经观察到大的负结磁阻，并归因于跨绝缘Cr2 Ge 2 Te 6层的自旋守恒隧穿输运。随着偏置的增加，会发生Fowler-Nordheim隧穿的交叉。隧穿磁电阻（TMR）的负符号表明Cr2 Ge 2 Te 6导带底部属于少数自旋，这与某些第一性原理计算的结果相反。这项工作表明，基于二维磁性绝缘体的vdW异质结构是一个有价值的平台，以获得进一步深入了解自旋极化隧穿输运，这是追求高性能自旋电子器件和各种量子现象的基础。
Intrinsic Spin Filter Effect in a $d$-wave altermagnet KV$_2$Se$_2$O with Open Fermi Surface
School of Science, Sun Yat-sen University（中山大学理学院）；Department of Physics and Astronomy, University of Florence（佛罗伦萨大学物理与天文学系）；Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University（武汉大学物理科学与技术学院人工微结构和量子调控教育部重点实验室）；The State Key Laboratory for Refractories and Metallurgy, Wuhan University of Science and Technology（武汉科技大学耐火材料与冶金国家重点实验室）；Laboratory for Computational Physical Sciences (MOE), State Key Laboratory of Surface Physics, and Department of Physics, Fudan University（复旦大学物理系表面物理国家重点实验室计算物理科学教育部重点实验室）；Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices, Sun Yat-sen University（中山大学广东省磁电物理与器件重点实验室）
Theory of tunnel magnetoresistance in magnetic tunnel junctions with hexagonal boron nitride barriers: mechanism and application to ferromagnetic alloy electrodes
National Institute for Materials Science (NIMS)（物质材料研究机构）；Kyoto Institute of Technology（京都工艺纤维大学）
Néel-Vector-Orientation Induced Direction-Robust Spin Filtering in Two-Dimensional Altermagnets
Shandong Institute of Advanced Technology（山东高等技术研究院）；Macao Polytechnic University（澳门理工大学）；Institute for Advanced Technology, Shandong University（山东大学先进技术研究院）；Uppsala University（乌普萨拉大学）
One-dimensional electronics with edge states in two-dimensional altermagnets
Singapore University of Technology and Design（新加坡科技设计大学）；Peking University（北京大学）；University of Wollongong（伍伦贡大学）；National University of Singapore（新加坡国立大学）
Tunnel Barrier to Spin Filter: Electronic Transport Characteristics of Transition Metal Atom Encapsulated in Smallest Cadmium Telluride Cage
我们报告了基于第一性原理理论的比较电子输运研究的原子链的Au，裸Cd 9 Te 9笼状团簇和单一的过渡金属（TM）（Ti，V，Cr，Mn，Fe，Co，Ni，Cu，Zn，Ru，Rh，Pd）原子封装在Cd 9 Te 9使用Au（111）作为电极。裸簇是半导体的，并且在特定的外加偏压下充当隧道势垒，并且在此之外，器件具有线性电流-电压关系。在器件的I-V特性曲线中，几种TM（Ti，V，Cr，Mn，Fe）材料表现出半金属特性和自旋过滤效应。对金属、半导体和半金属纳米结构的I-V特性进行了详细的定性和定量分析。
Extreme Strain Controlled Correlated Metal-Insulator Transition in the Altermagnet CrSb
KTH Royal Institute of Technology（瑞典皇家理工学院）；Leibniz Institute for Solid State and Materials Research, IFW Dresden（德累斯顿IFW莱布尼茨固体与材料研究所）；Center for High Pressure Science and Technology Advanced Research（高压科学与技术前沿研究中心）；Politecnico di Milano（米兰理工大学）；SLAC National Accelerator Laboratory（斯坦福直线加速器国家实验室）；Diamond Light Source（英国钻石光源）；Lund University（隆德大学）；Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所）
