2022 Outstanding Master Student Award － Ho Hoang Huy （Pham Laboratory）－

The ongoing development of artificial intelligent technologies has putted huge pressure of data storage industry. The experts forecasted that in the next ten years, the magnetic recording media must exceed 4 Tbpsi to meet the demand. Such a high areal density requires the magnetic reader to be smaller than 20 nm which is over the capability of current magnetic reader technology - tunneling magnetoresistance (TMR) reader. One of the biggest problem for TMR reader is the increasement of thermal noise when miniaturizing causing deterioration of signal-to-noise ratio. Moreover, due to the complicated structural design, it is technically challenging to reduce the size to less than 20 nm. To overcome the hurdle, a new generation of reader called spin-orbit torque (SOT) reader utilizing the inverse spin Hall effect was proposed to be the successor of TMR reader thanks to its simple structure and good scalability. This SOT reader simply consists of a spin Hall layer and a ferromagnetic layer. However, in the proof of concept using heavy metal as a spin Hall material, the output signal is insufficient to serve as the reader for beyond 4 Tbpsi hard disk drive reader due to the limited spin Hall angle of heavy metals.

In my Master thesis, we proposed the integration of BiSb topological insulator to the SOT reader. BiSb is a quantum material with gigantic spin Hall angle which can significantly elevate the output of the reader and provide sufficiently high signal-to-noise ratio. We successfully demonstrated a proof of concept of BiSb-based SOT reader with a giant inverse spin Hall angle of 61 and an output of 15 mV for 20×20 squared µm. Our device displayed an improvement of two million times stronger in terms of performance comparing to that in the heavy metal-based SOT reader. Our work has proved the capability of BiSb for the next generation of hard disk drive reader beyond 4 Tbpsi.

• Large inverse spin Hall effect in BiSb topological insulator for 4 Tb/in2 magnetic recording technology, Appl. Phys. Lett. 122, 052401(2023)

First and foremost, I would like to express my gratitude towards my academic advisor - Prof. Pham Nam Hai for his dedication during my Master study. Furthermore, I would like to thank the all the faculty members of Electrical and Electronic Engineering Department for providing me a wonderful course. I believe this course is the precious step to go further in this field as an engineer or as a researcher. The award is a recognition for the research conducted in the past two years and also an encouragement for my endeavor. Without the support of my beloved family, academic advisor, laboratory members, university staffs, and industrial partners, I could not have an opportunity to receive this award. I deeply send my appreciation towards everyone.