Topological antiferromagnetic spin valve

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In FM/NM/FM trilayers (FM: ferromagnet, NM: nonmagnet), the change of relative orientation between the two FM moments could lead to varying opposition to the tunneling current flow: this tunneling magnetoresistance (TMR) is proportional to the spin polarization of FMs as is characterized by the Julliere’s model, and thus it is not usually seen in antiferromagnets with negligible spin polarization. Here, we demonstrate the existence of antiferromagnetic TMR in a magnetic octupole valve Mn3Sn/MgO/Mn3Sn, supported by the theory. Remarkably, although the spin polarization rate is three orders smaller than that of Fe, Mn3Sn/MgO/Mn3Sn shows 5 times larger TMR than Fe/MgO/Mn3S. This emphasizes the dominant role of octupole polarization, instead of spin polarization.