Giant Spin Hall Effect and Switching Induced by Spin-Transfer Torque in a W / Co 40 Fe 40 B 20 / MgO Structure with Perpendicular Magnetic Anisotropy

We obtain robust perpendicular magnetic anisotropy in a β-W=Co40Fe40B20=MgO structure without the need of any insertion layer between W and Co40Fe40B20. This is achieved within a broad range of W thicknesses (3.0–9.0 nm), using a simple fabrication technique. We determine the spin Hall angle (0.40) and spin-diffusion length for the bulk β form of tungsten with a large spin-orbit coupling. As a result of the giant spin Hall effect in β-W and careful magnetic annealing, we significantly reduce the critical current density for the spin-transfer-torque-induced magnetic switching in Co40Fe40B20. The elemental β-W is a superior candidate for magnetic memory and spin-logic applications.

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