Anisotropic spin filtering by an altermagnetic barrier in magnetic tunnel junctions

作者：Boyuan Chi, Leina Jiang, Yu Zhu, Guoqiang Yu, Caihua Wan, Xiufeng Han · 发表于：Physical Review Applied · 年份：2025 · DOI：10.1103/physrevapplied.23.014013 · 被引用次数：26 · 研究领域：Magnetic properties of thin films、Quantum and electron transport phenomena、ZnO doping and properties

The spin-filtering effect, distinct decaying lengths experienced by oppositely-spin-polarized electrons in a magnetic barrier, generally occurs in ferromagnetic insulators or semiconductors. With the rise of altermagnetic (ALM) materials that exhibit similar capability of spin-polarizing electrons with ferromagnets, it is a natural question to ask whether ALM insulators or semiconductors can also act as unique barriers for the spin-splitting effect. Here, through first-principles calculations, we investigate the complex band structure of the ALM insulator ${\text{FeF}}_{2}$ and find that it possesses an anisotropic spin-filtering effect: along the [001] direction of ${\text{FeF}}_{2}$, a current remains spin neutral but has locally nonvanishing spin polarizations in the momentum space; moreover, along the [110] direction of ${\text{FeF}}_{2}$, 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 magnetic tunnel junction with an ALM barrier: ALM-electrode/ALM-insulator-barrier/nonmagnetic-electrode and ferromagnetic-electrode/ALM-insulator-barrier/nonmagnetic-electrode, using ${\text{RuO}}_{2}(001)/{\text{FeF}}_{2}/{\text{IrO}}_{2}$ and ${\text{CrO}}_{2}(110)/{\text{FeF}}_{2}/{\text{IrO}}_{2}$, respectively, as the corresponding prototypes. We found that these two proposed MTJs exhibited tunneling magnetoresistance ratios of 216% and 3956%, ...