High Entropy Alloy Thin Films as Efficient Spin-Orbit Torque Sources for Spintronic Memories

Abstract

High entropy alloys (HEAs) containing multiple elements are emerging as advanced materials with enhanced functionalities. However, their use for spintronic applications remains elusive. Here, it is demonstrated that iridium based HEAs, grown by magnetron sputtering at room temperature, can be used as spin Hall layers. These films display highly efficient conversion of charge current into spin current. They also allow for the epitaxial growth of magnetic multilayers with perpendicular magnetic anisotropy as well as synthetic antiferromagnets using a ternary RuAlGa antiferromagnetic coupling layer. It is demonstrated that iridium-based HEAs serve as effective sources of spin-orbit torque, as quantified by spin-torque ferromagnetic resonance and harmonic Hall measurements, enabling current-induced magnetization reversal and domain wall motion. The threshold current density for current-induced magnetization switching is found to be as low as ∼10 MA cm⁻² with reproducible deterministic switching, and that domain walls in HEA-based racetracks can be driven at speeds of up to 300 m s⁻¹ at a current density of 65 MA cm⁻². These results show that HEAs should be considered for high-performance spintronic applications.