A Potential Spin-orbit Torque Device using the Tri-layer Structure

Yuan-Chieh Tseng^1*, Chih-Wei Cheng¹, Yu-Han Huang¹, Wei-Jen Chan², Yi-Tsung Lin², Min-Cheng Chen², Yen-Wei Huang¹, Shou-Zen Chang², G. Chern²

¹Materials Science & Engineering, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
²Physics, National Chung Cheng University, Chiayi, Taiwan

* Presenter:Yuan-Chieh Tseng, email:yctseng1978@nycu.edu.tw

How to develop spin-orbit-torque (SOT) devices with the virtues of field-free, perpendicular anisotropy, and low switching current is one of the many challenges in spintronics today. We developed a CoFeB/Ta/CoFeB tri-layer SOT device that met the above requirements. The key to the success of this structure is to ensure that (i) changes of the inter-layer coupling (IEC) and CoFeB anisotropy can occur simultaneously; (ii) one of the CoFeB needs to have a slightly tilted moment in the beginning. When sufficient current is given, the SHE reverses the already-tilted CoFeB, and the other CoFeB can be reversed simultaneously by the IEC with the field-free nature. Adjusting the thickness of Ta can modify the coupling state to reduce switching current while the field-free nature was preserved. Micromagnetic simulation suggests that the Néel orange peel effect (NOPE) is non-negligible due to interface roughness and coupling effect in the presence of perpendicular anisotropy. Fortunately, the Néel field induced by the NOPE appears to favor the field-free reversal.

Keywords: spin-orbit torque, field-free, CoFeB, antiferromagnetic