Spin Hall effect from hybridized 3$d$-4$p$ orbitals

TL;DR

This paper demonstrates that a paramagnetic CoGa alloy can generate significant spin Hall effect and enable spin-orbit torque switching without heavy elements, due to hybridized 3d-4p orbitals, confirmed by experiments and first-principles calculations.

Contribution

It reveals that CoGa, lacking heavy elements, exhibits a large spin Hall angle driven by hybridized orbitals, enabling efficient spin current generation and SOT switching.

Findings

CoGa exhibits a spin Hall angle of +0.05±0.01.

Hybridized Co 3d - Ga 4p orbitals are responsible for SHE.

Efficient SOT switching achieved in CoGa/MnGa heterostructures.

Abstract

Electrical manipulation of magnetization by spin-orbit torque (SOT) has shown promise for realizing reliable magnetic memories and oscillators. To date, the generation of transverse spin current and SOT, whether it is of spin Hall effect (SHE), Rashba-Edelstein effect or spin-momentum locking origin, relies primarily on materials or heterostructures containing 5$d$ or 6$p$ heavy elements with strong spin-orbit coupling. Here we show that a paramagnetic CoGa compound possesses large enough spin Hall angle to allow robust SOT switching of perpendicularly-magnetized ferrimagnetic MnGa films in CoGa/MnGa/Oxide heterostructures. The spin Hall efficiency estimated via spin Hall magnetoresistance and harmonic Hall measurements is +0.05$\pm$0.01, which is surprisingly large for a system that does not contain any heavy metal element. First-principles calculations corroborate our experimental observations and suggest that the hybridized Co 3$d$ - Ga 4$p$ orbitals along R-X in the Brillouin zone is responsible for the intrinsic SHE. Our results suggest that efficient spin current generation can be realized in intermetallic by alloying a transition metal with a $p$-orbital element and by Fermi level tuning.