Efficient spin-orbit torque driven magnetization switching of GdFe using phosphorus-implanted platinum layers

Abstract: The capability of the spin-orbit torque (SOT) generated via phenomena such as the spin Hall effect in heavy metals, in switching the magnetization of an adjacent magnetic material, has been studied extensively over the last decade. The efficiency of SOT generation is commonly quantified in terms of the spin Hall angle {\theta}_SH. In this work, we demonstrate experimentally that implanting platinum (Pt) with phosphorus (P), resulting in Pt (P) d, where d denotes the implantation dose, increases {\theta}_SH by a factor of 7, from 0.06 (d = 0) to 0.43 (d = 10*10^16 ions/cm^2). The enhanced {\theta}_SH, along with factors such as perpendicular magnetic anisotropy and resistivity, lead to reduction of the critical current density for switching the perpendicular magnetization of ferrimagnetic rare earth-transition metal alloy Gd26Fe74, by a factor of nearly 27, from 4.0*1011 A/m^2 (d = 0) to 1.5*10^10 A/m^2 (d = 10*10^16 ions/cm^2). Further, the switching current density at zero thermal fluctuations and thermal stability factor were evaluated and found to be 2.0*10^10 A/m^2 and 61.4 (d = 10*10^16 ions/cm^2), with the latter being sufficiently above the required threshold for commercial memory applications. Our results suggest that Pt (P) could be a strong candidate in realizing efficient SOT driven magnetization switching leading to the development of improved memory and logic devices in the future.