Giant orbital torque-driven picosecond switching in magnetic tunnel junctions

Area of Science:

• Spintronics
• Materials Science
• Condensed Matter Physics

Background:

• Orbital effects and orbital torque (OT) represent a novel mechanism for manipulating magnetic moments.
• Current OT-based magnetic memory technologies face challenges with low orbital-to-spin conversion efficiency and magnetic tunnel junction (MTJ) incompatibility.

Purpose of the Study:

• To develop and demonstrate OT-MTJ devices overcoming existing limitations.
• To achieve efficient orbital-to-spin conversion and compatibility with MTJs for advanced magnetic memory applications.

Main Methods:

• Fabrication of OT-MTJ devices utilizing a Ru/W bilayer structure.
• Characterization of device performance, including effective spin-orbit Hall conductivity and switching dynamics.
• Experimental validation of picosecond switching using short electrical pulses.

Main Results:

• Achieved a giant orbital torque with an effective spin-orbit Hall conductivity of -12,600 ħ/2e Ω⁻¹ cm⁻¹.
• Demonstrated >90% orbital-to-spin conversion efficiency in the α-W layer due to significant orbit-spin diffusivity.
• Successfully switched OT-MTJs using pulses as short as 28.7 ps, showing picosecond-scale dynamics.
• Observed a 5-8x reduction in driving voltage compared to β-W-based devices and a uniform resistance distribution (<1 Ω).

Conclusions:

• The developed Ru/W-based OT-MTJ devices exhibit giant orbital torque, overcoming previous efficiency and compatibility issues.
• These findings pave the way for practical applications of orbital effects in high-performance magnetic memory technologies.
• The study bridges the gap between fundamental orbital physics and the development of next-generation magnetic memory devices.