Significant enhancement of spin-orbit torque efficiency by optimizing the interlayer thickness in [Pt/Ru]_n/Pt multilayers

Spin-orbit torque (SOT) is a promising strategy for switching magnetization for magnetic random access memory and maintaining magnetization coherent precession for magnetic nano-oscillator or magnon-based logic device applications. Thus, the enhancement of SOT efficiency is the crucial point for the implementation of high-performance SOT devices. Here, we demonstrate that the effective damping-like SOT efficiency xi(DL) in the periodic [Pt(2 nm)/Ru(1 nm)](n)Pt(2 nm) multilayers with a low resistivity of similar to 40 mu Omega cm (comparable to 23 mu Omega cm of the pure Pt film) exhibits an over 100% enhancement compared to that of the pure 12 nm thick Pt (xi(DL) = 0.055) at the periodic number n = 3, even reaches 0.257 (similar to 360% enhancement) determined by damping dc modulation method at [Pt/Ru] total thickness of 32 nm with n = 10. Our findings will benefit various SOT devices by significantly reducing energy consumption.