Insertion Effects on the Ferromagnet/Topological Heterostructure’s Spin-orbit Torque Efficiency

Yu-Lon Lin^1*, Yuan-Chieh Tseng¹

¹Department of Materials Science & Engineering, National Yang Ming Chiao Tung University, Hsinchu, Taiwan

* Presenter:Yu-Lon Lin, email:yulon0908@gmail.com

Topological insulators (TIs) are a group of quantum materials, which have gained great interest due to their exotic transport properties and ultra-large spin to charge conversion efficiency. So far, most TIs thin films were grown by the molecular beam epitaxy (MBE) method, which is not compatible in the semiconductor industry with mass production. Here, we have successfully fabricated the Bi₂Se₃/Ta/CoFeB heterostructures with different Ta thickness by magnetron sputtering, which is an industry-friendly technique. X-ray magnetic circular dichroism experiments have been performed to investigate the role of the HM insertion layer in terms of the atomics moment in Bi₂Se₃/Ta/CoFeB heterostructures. The results reveal that enhancement of both spin and orbital moments was obtained via interfacial engineering. Furthermore, the spin-orbit torque efficiency of Bi₂Se₃/Ta/CoFeB was determined to be as large as 3.3 using second harmonic Hall methods, which is comparable to those TIs grown by MBE and significantly larger than those of heavy metals. Our work demonstrates that the thin HM insertion can suppress the intermixing at the FM/TIs interface and, therefore, improves the magnetic properties of the top FM layer, which is promising for the development of SOT-MRAM and next-generation spintronic logic devices.

Keywords: Topological insulators, Spin-orbit torque, X-ray magnetic circular dichroism, Interfacial engineering