Enhancing the spin–orbit torque efficiency in Pt/CoFeB/Pt based perpendicularly magnetized system

Abstract

In the recent past, current-induced magnetization reversal (CIMR) has been extensively studied on the heterostructures prepared with heavy metal (HM) and ferromagnet (FM) having spin–orbit torque (SOT). The critical current density (Jc) for magnetization switching depends on the SOT efficiency. In this study, we have chosen Ta/Pt/CoFeB/Pt/Ta/CoFeB/Pt heterostructure having perpendicular magnetic anisotropy (PMA) with broken lateral symmetry and an in-plane magnetized (IMA) ferromagnetic layer on top of the Ta layer. In this heterostructure, we have utilized the SOT originated by the spin-Hall effect that arises from two materials having opposite spin Hall angles i.e. the bottom Pt and the top Ta layer. We have also introduced lateral space inversion asymmetry (SIA) that combines both damping-like and field-like field. The enhanced spin Hall angle, the stray field by IMA ferromagnetic layer, and the lateral SIA effect jointly enhances the SOT efficiency of the system to reduce the Jc for CIMR. We have found that the SOT efficiency and the effective spin Hall angle of our newly designed heterostructure to be 106 Oe/1011A/m2 and 0.23, respectively. Thus we have achieved CIMR with a lower critical current density of 8.65×1010 A/m2 and 3.35×1010 A/m2 at 0 Oe and 600 Oe field applied in-plane (IP), respectively. Due to the lower Jc for CIMR our newly designed heterostructure has potential in low-power magnetic data storage applications.