近日，日本东京大学教授Satoru Nakatsuji及其研究团队发现了反铁磁隧道结中的八极驱动磁电阻。这一研究成果于2023年1月18日发表在国际顶尖学术期刊《自然》上。

该研究组报道了由Mn₃Sn/MgO/Mn₃Sn组成的全反铁磁隧道结的TMR观测。研究人员在室温下测量了约2%的TMR比，这出现在手性反铁磁状态下的平行和反平行磁八极之间。

此外，研究人员使用Fe/MgO/Mn₃Sn MTJ进行了测量，并表明反铁磁体中各向异性纵向自旋极化电流的符号和方向可以由八极方向控制。值得注意的是，全反铁磁MTJ的TMR比(约2%)远远大于观测到的自旋极化的估计。从理论上讲，课题组发现手性反铁磁MTJ可以产生一个相当大的TMR比，这是由于时间反转、对称破缺极化的特性。他们的工作为超快和高效的反铁磁自旋电子器件的发展奠定了基础。

据了解，通过磁隧道结(MTJ)的隧穿电流强烈依赖于夹在绝缘势垒中的铁磁电极中磁化的相对方向，从而提供自旋电子学器件的有效读出。隧穿磁阻(TMR)被认为与界面处的自旋极化成正比，迄今为止主要在铁磁体中研究。

附：英文原文

Title: Octupole-driven magnetoresistance in an antiferromagnetic tunnel junction

Author: Chen, Xianzhe, Higo, Tomoya, Tanaka, Katsuhiro, Nomoto, Takuya, Tsai, Hanshen, Idzuchi, Hiroshi, Shiga, Masanobu, Sakamoto, Shoya, Ando, Ryoya, Kosaki, Hidetoshi, Matsuo, Takumi, Nishio-Hamane, Daisuke, Arita, Ryotaro, Miwa, Shinji, Nakatsuji, Satoru

Issue&Volume: 2023-01-18

Abstract: The tunnelling electric current passing through a magnetic tunnel junction (MTJ) is strongly dependent on the relative orientation of magnetizations in ferromagnetic electrodes sandwiching an insulating barrier, rendering efficient readout of spintronics devices1,2,3,4,5. Thus, tunnelling magnetoresistance (TMR) is considered to be proportional to spin polarization at the interface1 and, to date, has been studied primarily in ferromagnets. Here we report observation of TMR in an all-antiferromagnetic tunnel junction consisting of Mn3Sn/MgO/Mn3Sn (ref. 6). We measured a TMR ratio of around 2% at room temperature, which arises between the parallel and antiparallel configurations of the cluster magnetic octupoles in the chiral antiferromagnetic state. Moreover, we carried out measurements using a Fe/MgO/Mn3Sn MTJ and show that the sign and direction of anisotropic longitudinal spin-polarized current in the antiferromagnet7 can be controlled by octupole direction. Strikingly, the TMR ratio (about 2%) of the all-antiferromagnetic MTJ is much larger than that estimated using the observed spin polarization. Theoretically, we found that the chiral antiferromagnetic MTJ may produce a substantially large TMR ratio as a result of the time-reversal, symmetry-breaking polarization characteristic of cluster magnetic octupoles. Our work lays the foundation for the development of ultrafast and efficient spintronic devices using antiferromagnets8,9,10.

DOI: 10.1038/s41586-022-05463-w

Source: https://www.nature.com/articles/s41586-022-05463-w