† These authors contributed equally to this work Electrical manipulation of magnetization by spin-orbit torque (SOT) 1-6 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) 2,7 , Rashba-Edelstein effect 8 or spinmomentum locking origin 3,9 , relies primarily on materials or heterostructures containing 5d or 6p 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±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 3d -Ga 4p 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. * yongchang.
We fabricated (001)-oriented C1b-NiMnSb epitaxial films on MgO substrate by a magnetron sputtering system and systematically investigated the structure, magnetic property, and anisotropic magnetoresistance (AMR) effect. NiMnSb film was deposited using a stoichiometric NiMnSb target which has Mn-deficient (Mn ∼ 28.7 at. %) off-stoichiometric composition ratio. We have investigated bulk spin-polarization in NiMnSb films by measuring AMR on the basis of recent study for half-metallic L21-Heusler compounds. Although the negative sign of AMR ratio, which is indicative of half-metallic nature, was observed in the single layer NiMnSb films, the magnitude of AMR ratio (−0.10% at RT) was about half of the largest value reported for half-metallic L21-Heusler compounds. The current-perpendicular-to-plane (CPP) giant magnetoresistance (GMR) devices of NiMnSb/Ag/NiMnSb show MR ratio of 13.2% at 10 K and 4.2% at 300 K, which is higher than the previous result for NiMnSb/Cu/NiMnSb CPP-GMR devices [Caballero et al., J. Magn. Magn. Mater. 198–199, 55 (1999)], but much less than the CPP-GMR using L21-Heusler electrodes. The reduction of intrinsic bulk spin-polarization originating from the Mn-deficiency in NiMnSb layer is expected to be the main reason for small MR values.
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