标题： 具有绝缘交替磁铁的自旋过滤 显示英文标题

标题： Spin filtering with insulating altermagnets

摘要： 反磁性（AM）材料由于其电子能带结构中非相对论动量相关的自旋分裂最近引起了广泛关注，这可能对反铁磁（AFM）自旋电子学有用。然而，迄今为止，大多数研究都集中在可以用于自旋电子器件的AM金属上，例如反铁磁隧道结（AFMTJs）。与此同时，在反铁磁自旋电子学领域，AM绝缘体尚未得到充分探索。在这里，我们提出利用AM绝缘体（AMIs）作为高效的自旋过滤材料。通过分析二氧化钛型反磁体$MF_2$ ($M$ = $Fe, Co, Ni$) 的复杂能带结构，我们证明了这些AMIs中的倏逝态表现出自旋和动量依赖的衰减率，从而导致隧穿电流具有显著的动量依赖自旋极化。利用一个基于自旋依赖势垒的隧穿模型，我们估计了包括两个磁解耦的 $MF_2$ (001) 障碍层的自旋过滤磁性隧道结（SF-MTJs）中的TMR效应。我们预测基于AMIs$CoF_2$和$NiF_2$的SF-MTJs中，如果费米能级调整到接近价带顶，则自旋过滤TMR比值可达约150%-170%。我们的结果表明，AMIs为传统的铁磁或亚铁磁自旋过滤材料提供了一种可行的替代方案，可能推动下一代反铁磁自旋电子器件的发展。 显示英文摘要

摘要： Altermagnetic (AM) materials have recently attracted significant interest due to the non-relativistic momentum-dependent spin splitting of their electronic band structure which may be useful for antiferromagnetic (AFM) spintronics. So far, however, most research studies have been focused on AM metals which can be utilized in spintronic devices, such as AFM tunnel junctions (AFMTJs). At the same time, AM insulators have remained largely unexplored in the realm of AFM spintronics. Here, we propose to employ AM insulators (AMIs) as efficient spin-filter materials. By analyzing the complex band structure of rutile-type altermagnets $MF_2$ ($M$ = $Fe, Co, Ni$), we demonstrate that the evanescent states in these AMIs exhibit spin- and momentum-dependent decay rates resulting in a substantial momentum-dependent spin polarization of the tunneling current. Using a model of spin-filter tunneling across a spin-dependent potential barrier, we estimate the TMR effect in spin-filter magnetic tunnel junctions (SF-MTJs) that include two magnetically decoupled $MF_2$ (001) barrier layers. We predict a sizable spin-filter TMR ratio of about 150-170% in SF-MTJs based on AMIs $CoF_2$ and $NiF_2$ if the Fermi energy is tuned to be close to the valence band maximum. Our results demonstrate that AMIs provide a viable alternative to conventional ferromagnetic or ferrimagnetic spin-filter materials, potentially advancing the development of next-generation AFM spintronic devices.