Comparative Study of Current-Induced Torque in Cr/CoFeB/MgO and W/CoFeB/MgO.

Area of Science:

• Condensed matter physics
• Materials science
• Spintronics

Background:

• Orbital torque (OT) is debated for magnetic heterostructures, contrasting with spin-orbit torque (SOT).
• SOT is a promising mechanism for next-generation magnetoresistive random access memories (MRAM).

Purpose of the Study:

• To compare OT and SOT in representative systems (Cr/CoFeB/MgO and W/CoFeB/MgO).
• To investigate the potential emergence of OT in archetypal SOT stacks.

Main Methods:

• Fabrication and characterization of Cr/CoFeB/MgO and W/CoFeB/MgO heterostructures.
• Systematic variation of layer thicknesses (Cr, CoFeB, W).
• Torque measurements and analysis.

Main Results:

• Cr/CoFeB/MgO demonstrated substantial torque, comparable to or exceeding W/CoFeB/MgO, especially with thicker Cr and CoFeB layers.
• W/CoFeB/MgO showed a sign change in torque with increasing W and CoFeB thicknesses.
• Evidence suggests a mechanism crossover from SOT to OT in W/CoFeB/MgO.

Conclusions:

• Orbital torque can be significant in magnetic heterostructures, rivaling spin-orbit torque.
• Spin-orbit torque systems may exhibit orbital torque under specific thickness conditions.
• Findings clarify opportunities and challenges for SOT and OT in spintronic devices.