Enhanced Spin–Orbit Torques in Graphene by Pt Adatoms Decoration

Abstract

Graphene (Gr) with widely acclaimed characteristics, such as exceptionally long spin diffusion length at room temperature, provides an outstanding platform for spintronics. However, its inherent weak spin-orbit coupling (SOC) has limited its efficiency for generating the spin currents in order to control the magnetization switching process for the application in spintronics memories. Following the theoretical prediction on the enhancement of SOC in Gr by heavy atoms adsorption, here we experimentally observe a sizeable spin-orbit torques (SOTs) in Gr by the decoration of its surface with Pt adatoms in Gr/Pt(t Pt )/FeNi trilayers with the optimal damping-like SOT efficiency around 0.55 by 0.6-nm-thick Pt layer adsorption. The value is nearly four times larger than that of the Pt/FeNi sample without Gr and nearly twice as large as that of the Gr/FeNi sample without Pt adsorption. The efficiency of the enhanced SOT in Gr by Pt adatoms is also demonstrated by the field-free SOT magnetization switching process with a relatively low critical current density around 5.4 MA/cm2 in Gr/Pt/FeNi trilayers with the in-plane magnetic anisotropy. These findings pave the way for Gr spintronics application, offering solutions for future low power consumption memories.