Giant, Linearly Increasing Spin-Orbit Torque Efficiency in Symmetry-Broken Spin-Orbit Torque Superlattices

Area of Science:

• Materials Science
• Condensed Matter Physics
• Spintronics

Background:

• Magnetic heterostructures are crucial for spintronic technologies.
• High spin-orbit torque (SOT) efficiency and low impedance are desired for low-power applications.
• Conventional heterostructures often lack sufficient SOT efficiency.

Purpose of the Study:

• To engineer a symmetry-broken spin-orbit superlattice with enhanced SOT efficiency.
• To investigate the relationship between superlattice structure and SOT performance.
• To explore potential applications in low-power electronics and thermoelectrics.

Main Methods:

• Fabrication of [Pt_0.75Cu_0.25/Co/Ta]_n superlattices with varying repeat numbers (n).
• Characterization of spin-orbit torque efficiency and damping.
• Measurement of anomalous Nernst effect and resistivity.

Main Results:

• SOT efficiency increases linearly with repeat number 'n', reaching >200% at n=16.
• The enhanced SOT originates primarily from the spin Hall effect in Pt_0.75Cu_0.25.
• Anomalous Nernst effect shows a remarkable increase with 'n', highlighting the importance of thermal effects.

Conclusions:

• The [Pt_0.75Cu_0.25/Co/Ta] superlattice demonstrates a giant SOT effect, significantly outperforming conventional heterostructures.
• The material exhibits low resistivity and a strong anomalous Nernst effect.
• This superlattice holds great potential for low-power memory/logic devices and thermoelectric applications.