Spin-Orbit Torques in NbSe₂/Permalloy Bilayers

Area of Science:

• Condensed Matter Physics
• Materials Science
• Spintronics

Background:

• Spin-orbit torques are crucial for next-generation memory and logic devices.
• Transition-metal dichalcogenides (TMDs) are promising materials for spintronic applications.
• Understanding torque generation mechanisms in novel materials like NbSe2 is essential.

Purpose of the Study:

• To investigate current-induced spin-orbit torques generated by NbSe2.
• To characterize the nature and magnitude of these torques in NbSe2/Permalloy bilayers.
• To explore potential origins of observed torque components, including symmetry considerations.

Main Methods:

• Utilized spin-torque ferromagnetic resonance (ST-FMR) technique.
• Fabricated NbSe2/Permalloy bilayers for device measurements.
• Analyzed torque components including Oersted, antidamping, and field-like torques.

Main Results:

• Observed out-of-plane Oersted torque and in-plane antidamping torque with conductivity σS ≈ 10^3 (ℏ/2e)(Ωm)^-1.
• Detected a weak out-of-plane field-like torque opposing the Oersted torque.
• Measured a sample-dependent in-plane field-like torque, potentially linked to strain-induced symmetry breaking.

Conclusions:

• NbSe2 exhibits significant spin-orbit torque properties.
• Strain may play a critical role in generating unconventional torques in NbSe2 devices.
• Further research is needed to fully elucidate the strain-induced torque mechanisms.