Lee Hsun Lecture Series

Topic: Effective electrical manipulation of non-colinear antiferromagnetic order

Speaker: Prof. Chen Jingsheng

Department of Materials Science and Engineering,National University of Singapore

Time: 10:00-11:30,(Wed.) Dec. 24th,2025

Venue: Room 468, Lee Hsun Building, IMR CAS

Abstract:

Antiferromagnet as an active component in devices has recently been attracting intense attention due to its negligible stray field and ultra-fast magnetic dynamics,making it very promising for the high-density and fast-speed memory devices. The switching of antiferromagnetic (AFM) order by current induced spin-orbit torque (SOT) has already been realized. However,the critical switching current density should be further reduced for energy efficient memory. Furthermore,SOT-induced bidirectional switching of AFM order in perpendicular geometry,especially in the absence of external magnetic field,remain unveiled,which is essential for the practical application.  Recent works suggest that current-induced orbital Hall effect (OHE) can effectively manipulate the ferromagnetic order, thanks to the high orbital torque generation efficiency. In this presentation, I will report demonstration of deterministic switching of antiferromagnetic order in Weyl semimetal Mn₃Sn by OHE originated from metal Mn or oxide CuO_x. While Mn₃Sn is proven to be able to convert orbit torques to spin torques by itself, we find that inserting a heavy metal layer like Pt with proper thickness can effectively reduce the critical switching current density and improve the switching efficiency. Furthermore, we experimentally demonstrate field-free perpendicular switching of the magnetic octupole m_oct in chiral AFM Mn₃Sn by combining in-plane and out-of-plane SOTs generated by two-dimensional van-der Vaals WTe₂. The out-of-plane SOT breaks the in-plane inversion symmetry and leads to deterministic bidirectional switching of m_oct in polycrystalline Mn₃Sn even without a fixed perpendicular m_oct easy axis. The switching ratio reaches up to 80% instead of commonly reported 20-30% in polycrystalline Mn₃Sn and the critical current density is also reduced to the order of 1 MA/cm².