Anomalous decrease in effective damping parameter αeff 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 αeff, which is also referred to as anti-damping effect, is found to be critically dependent on the thickness of β-Ta layer; αeff 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 (tTa) revealed an anomalous negative interfacial spin mixing conductance, and spin diffusion length,. The increase in αeff observed above tTa = 6 nm is attributed to the weakening of SOT at higher tTa. 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.
A damping-like
spin-orbit torque (SOT) is a prerequisite for ultralow-power
spin logic devices. Here, we report on the damping-like SOT in just
one monolayer of the conducting transition-metal dichalcogenide (TMD)
TaS
2
interfaced with a NiFe (Py) ferromagnetic layer. The
charge-spin conversion efficiency is found to be 0.25 ± 0.03
in TaS
2
(0.88)/Py(7), and the spin Hall conductivity
is found to be superior to values reported
for other TMDs. We also observed sizable field-like torque in this
heterostructure. The origin of this large damping-like SOT can be
found in the interfacial properties of the TaS
2
/Py heterostructure,
and the experimental findings are complemented by the results from
density functional theory calculations. It is envisioned that the
interplay between interfacial spin–orbit coupling and crystal
symmetry yielding large damping-like SOT. The dominance of damping-like
torque demonstrated in our study provides a promising path for designing
the next-generation conducting TMD-based low-powered quantum memory
devices.
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