Chou Chung-Tao, Ghosh Supriya, McGoldrick Brooke C, Nguyen Thanh, Gurung Gautam, Tsymbal Evgeny Y, Li Mingda, Mkhoyan K Andre, Liu Luqiao
Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA.
Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, USA.
Nat Commun. 2024 Sep 7;15(1):7840. doi: 10.1038/s41467-024-52208-6.
Efficient detection of the magnetic state is a critical step towards useful antiferromagnet-based spintronic devices. Recently, finite tunneling magnetoresistance (TMR) has been demonstrated in tunnel junctions with antiferromagnetic electrodes, however, these studies have been mostly limited to junctions with two identical antiferromagnet (AFM) electrodes, where the matching of the spin-split Fermi surfaces played critical role. It remains unclear if AFMs can provide a finite net spin polarization, and hence be used as a spin polarizer or detector. In this work, we experimentally fabricate single-sided antiferromagnetic tunnel junctions consisting of one AFM electrode (MnSn) and one ferromagnet (FM) electrode (CoFeB), where the spin polarized tunneling transport from AFM is detected by the FM layer. We observe a high TMR at cryogenic temperature (>100% at 10 K) in these asymmetric AFM tunnel junctions, suggesting a large effective spin polarization from MnSn despite its nearly vanishing magnetization. The large TMR is consistent with recent theoretical studies where the broken symmetry in non-collinear AFMs is predicted to lift the spin degeneracy in the band structure. Our work provides strong evidence that spin polarized electrical transport can be achieved from AFMs.
高效检测磁状态是迈向实用的基于反铁磁体的自旋电子器件的关键一步。最近，在具有反铁磁电极的隧道结中已证实存在有限的隧穿磁电阻（TMR），然而，这些研究大多局限于具有两个相同反铁磁体（AFM）电极的结，其中自旋分裂费米面的匹配起着关键作用。目前尚不清楚反铁磁体是否能提供有限的净自旋极化，从而用作自旋极化器或探测器。在这项工作中，我们通过实验制备了由一个AFM电极（MnSn）和一个铁磁体（FM）电极（CoFeB）组成的单面反铁磁隧道结，其中FM层检测来自AFM的自旋极化隧穿输运。我们在这些不对称AFM隧道结的低温下（10 K时>100%）观察到高TMR，这表明尽管MnSn的磁化几乎消失，但其仍具有较大的有效自旋极化。这种大的TMR与最近的理论研究一致，在这些研究中预测非共线反铁磁体中的对称性破缺会消除能带结构中的自旋简并。我们的工作提供了强有力的证据，表明反铁磁体可以实现自旋极化的电输运。
