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

Abstract

We report modulated switching current density and spin-orbit torques (SOT) in MnGa/Ta films with inserting very thin Co 2 FeAl and Co layers. Ferromagnetic coupling has been found in MnGa/Co 2 FeAl/Ta, resulting in a decreased effective anisotropy field. On the contrary, in MnGa/Co/Ta, antiferromagnetic coupling plays a dominant role. The switching current density J c in MnGa/Ta is 8.5 × 10 7 A/cm 2. After inserting 0.8-nm-Thick Co 2 FeAl and Co, theJ c becomes 5 × 10 7 A/cm 2 and 9 × 10 7 A/cm 2, respectively. By performing adiabatic harmonic Hall voltage measurements, it is demonstrated that the inserted Co 2 FeAl layer has mainly enhanced the field-like torques, while in MnGa/Co/Ta the damping-like torques have been enhanced. Finally, the enhanced spin Hall effect (SHE) has also been studied using the spin Hall magnetoresistance measurement. The modulated J c and SOT are ascribed to the combination of magnetic coupling, Rashba effect and SHE at the interfaces.