Energy-Efficient Single Layer Spin Hall Nano-Oscillators Driven by Berry Curvature

Area of Science:

• Spintronics
• Condensed Matter Physics
• Materials Science

Background:

• Spin Hall nano-oscillators (SHNOs) show promise for microwave generation and computing.
• Current SHNOs face challenges like high energy use and difficulties in fabricating high-quality thin films.
• Topological magnetic Weyl semimetals offer potential solutions due to intrinsic ferromagnetism and large spin-orbit coupling.

Purpose of the Study:

• To develop high-quality single-layer epitaxial ferromagnetic Weyl semimetal thin films for SHNOs.
• To investigate the spin Hall conductivity of these materials.
• To demonstrate self spin-orbit torque driven magnetization auto-oscillations in these SHNOs.

Main Methods:

• Fabrication of single-layer epitaxial ferromagnetic Co2MnGa Weyl semimetal thin films.
• Measurement of spin Hall conductivity using experimental techniques.
• Theoretical calculations to understand the origin of large spin Hall conductivity.
• Demonstration of auto-oscillations driven by spin-orbit torque.

Main Results:

• Achieved a giant spin Hall conductivity (σSHC = (6.08 ± 0.02) × 10^5 (ℏ/2e) Ω^-1 m^-1), an order of magnitude higher than previous reports.
• Experimental results corroborated by theoretical calculations showing large intrinsic spin Hall conductivity due to strong Berry curvature.
• Demonstrated self spin-orbit torque driven magnetization auto-oscillations for the first time.
• Achieved an ultralow threshold current density (Jth = 6.2 × 10^11 A m^-2) for auto-oscillations.

Conclusions:

• Single-layer magnetic Weyl semimetals are promising for developing energy-efficient spintronic devices.
• The observed giant spin Hall conductivity and ultralow threshold current density highlight the potential of these materials for advanced spintronic applications.
• This work addresses challenges in thin film growth and demonstrates a viable path towards practical SHNOs.