摘要：Anomalous decrease in effective damping parameter α eff in sputtered Ni81Fe19 (Py) thin films in contact with a very thin β -Ta layer without necessitating the flow of DC-current is observed. This reduction in α eff , which is also referred to as anti-damping effect, is found to be critically dependent on the thickness of β -Ta layer; α eff being highest, i.e., 0.0093 ± 0.0003 for bare Ni81Fe19(18 nm)/SiO2/Si compared to the smallest value of 0.0077 ± 0.0001 for β- Ta(6 nm)/Py(18 nm)/SiO2/Si. This anomalous anti-damping effect is understood in terms of interfacial Rashba effect associated with the formation of a thin protective Ta2O5 barrier layer and also the spin pumping induced non-equilibrium diffusive spin-accumulation effect in β- Ta layer near the Ta/Py interface which induces additional spin orbit torque (SOT) on the moments in Py leading to reduction in . The fitting of ( t Ta ) revealed an anomalous negative interfacial spin mixing conductance, and spin diffusion length, . The increase in α eff observed above t Ta = 6 nm is attributed to t he weakening of SOT at higher t Ta . The study highlights the potential of employing β- Ta based nanostructures in developing low power spintronic devices having tunable as well as low value of α.
