Ultralarge Spin Hall Angle via TiO₂ Nanocluster-Mediated Side-Jump Scattering

Area of Science:

• Materials Science
• Condensed Matter Physics
• Spintronics

Background:

• Spin-orbit torque (SOT) is crucial for efficient magnetization switching in spintronic devices.
• Existing heavy metal materials for SOT present limitations in spin Hall angle, conductivity, and fabrication.
• There is a need for advanced materials offering superior SOT performance and practical applicability.

Purpose of the Study:

• To develop and characterize novel W_1-x(TiO₂)_x nanocomposites for enhanced SOT efficiency.
• To investigate the underlying mechanisms responsible for the improved SOT performance.
• To evaluate the potential of these nanocomposites for industrial applications, particularly in magnetic random-access memory (MRAM).

Main Methods:

• Fabrication of W_1-x(TiO₂)_x nanocomposites by incorporating TiO₂ nanoclusters into β-phase tungsten.
• Experimental measurement of spin Hall angle and damping-like SOT efficiency.
• Theoretical analysis to differentiate intrinsic and extrinsic contributions to the spin Hall effect.
• Demonstration of current-induced magnetization switching and measurement of critical switching current density.

Main Results:

• Achieved a maximum spin Hall angle of -1.66 and damping-like SOT efficiency of -0.94 in W_0.88(TiO₂)_0.12.
• Demonstrated a 114% enhancement in SOT efficiency compared to pure tungsten.
• Identified substantial side jump induced by TiO₂ nanoclusters as the primary source of efficiency enhancement.
• Observed ultralow critical current density of 1.78 × 10⁶ A cm^-2 for magnetization switching.

Conclusions:

• W_1-x(TiO₂)_x nanocomposites offer significantly enhanced SOT efficiency due to extrinsic side jump effects.
• The ultralow critical current density and cost-effectiveness make W_0.88(TiO₂)_0.12 a promising alternative to conventional β-W.
• These findings pave the way for practical industrial applications of SOT-MRAM technology.