Modulated switching current density and spin-orbit torques in MnGa/Ta films with inserting ferromagnetic layers

Area of Science:

• Spintronics
• Materials Science
• Condensed Matter Physics

Background:

• Spin-orbit torques (SOT) are crucial for efficient manipulation of magnetic states in spintronic devices.
• The switching current density (Jc) in magnetic films dictates the energy efficiency of magnetic memory and logic operations.
• Interface engineering in heterostructures offers a pathway to tune magnetic and spintronic properties.

Purpose of the Study:

• To investigate the effect of inserting ultrathin Co2FeAl and Co layers on the switching current density and SOT in MnGa/Ta films.
• To understand the role of magnetic coupling (ferromagnetic vs. antiferromagnetic) at the interfaces on the observed phenomena.
• To explore the contribution of the spin Hall effect (SHE) and Rashba effect to the modulated SOT.

Main Methods:

• Fabrication of MnGa/Ta, MnGa/Co2FeAl/Ta, and MnGa/Co/Ta thin film heterostructures.
• Measurement of switching current density (Jc) using electrical transport techniques.
• Characterization of spin-orbit torques (SOT) via adiabatic harmonic Hall voltage measurements.
• Investigation of the spin Hall effect (SHE) using spin Hall magnetoresistance (SMR) measurements.

Main Results:

• Insertion of 0.8-nm-thick Co2FeAl reduced Jc to 5 × 10^7 A/cm^2, while Co insertion resulted in Jc of 9 × 10^7 A/cm^2, compared to 8.5 × 10^7 A/cm^2 for MnGa/Ta.
• Ferromagnetic coupling in MnGa/Co2FeAl/Ta decreased effective anisotropy, enhancing field-like torques.
• Antiferromagnetic coupling in MnGa/Co/Ta dominated, enhancing damping-like torques.
• Enhanced SHE was observed and quantified through SMR measurements.

Conclusions:

• The switching current density and SOT in MnGa/Ta films can be effectively modulated by inserting ultrathin Co2FeAl and Co layers.
• The observed modulations are attributed to a combination of interfacial magnetic coupling, Rashba effect, and the spin Hall effect.
• This study demonstrates a viable strategy for optimizing SOT efficiency and reducing switching currents in spintronic devices.