STUDY OF SPIN-ORBIT TORQUE IN FERROMAGNETIC HETEROSTRUCTURES AND RELATED DEVICE APPLICATIONS

Abstract

Spin-orbit torque (SOT) induced by an in-plane charge current offers an alternative way to manipulate magnetization. To reduce power consumption of SOT-based devices, extensive research has been conducted to study the charge-spin conversion. In this context, this thesis firstly presents an in-situ study of oxygen on the SOT and current-induced switching in Pt/Co bilayers via controlled oxygen exposure in an ultrahigh vacuum system. It is found that the reduction in switching current density by oxygen exposure is caused by the combined effect of increase in SOT and lowering of switching energy barrier for incoherent switching. Finally, we propose and experimentally demonstrate a spin torque gate magnetic sensor using the WTex/Ti/CoFeB structure with both perpendicular magnetic anisotropy and large damping-like SOT. Driven by an ac current, and with the Hall voltage averaged over many cycles, the sensor can generate a linear response to the magnetic field with zero offset.