ABSTARCT:

There are two problems to be overcome for the strong-coupling synthetic antiferromagnetic structure with perpendicular magnetic anisotropy to serve as spin-orbit-torque-based memory and logic devices: first, the Hall signals of the two ferromagnetic layers in the synthetic antiferromagnetic structure are usually weakened by each other, which is not beneficial to the use of Hall voltage to read ; secondly, it is usually necessary to apply a large in-plane auxiliary magnetic field to obtain the deterministic magnetization switching caused by the spin orbit torque. In order to solve these two problems, we prepared CoPt/Ru/CoTb and CoPt/Ru/CoPt synthetic antiferromagnetic heterojunctions. By controlling the long-ranged interlayer exchange coupling and the neighboring ferrimagnetic coupling, we integrate the advantages of ferromagnetic CoPt, ferrimagnetic CoTb, and interlayer antiferromagnetic CoPt/Ru/CoTb spin configurations into a heterojunction. In the CoPt/Ru/Co65Tb35 heterojunction with macroscopic interlayer antiferromagnetic coupling, the compensation of magnetization at room temperature and the enhancement of residual anomalous Hall resistance are simultaneously realized. Moreover, it is proved theoretically and experimentally that the magnetic-field-free magnetization switching in CoPt/Ru/CoPt can be induced by the spin orbit torque when there is a significant difference in the Dzyaloshinsky Moriya interaction between the lower magnetic layer and the upper magnetic layer of the synthetic antiferromagnet. These findings provide key insights for understanding the role of spin orbit torque and Dzyaloshinsky Moriya interaction in perpendicular magnetization switching of magnetically coupled chiral system, and pave the way to practical applications of synthetic antiferromagnets.

BIOGRAPHY:

Prof. Shishen Yan is a distinguished professor at Shandong University, where he serves as a member of the Academic Committee. He earned his Ph.D. in Physics from Shandong University and was a Humboldt Scholar at the Jülich Research Center in Germany, working under Nobel Laureate Peter Grünberg. His research focuses on spintronics, magnetic semiconductors, and multilayer magnetic films. He has established a spintronics laboratory at Shandong University, contributing significantly to the field through his work on magnetic nanomaterials and spin injection in semiconductors.