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In this study, we investigate the spin Hall effect in heterostructures of Bi0.85Sb0.15 (10 nm) topological insulator/Ru(Ti)/Ta/Co20Fe60B20/MgO with perpendicular magnetic anisotropy. By optimizing the Ru (Ti) interfacial layer thickness as well as deposition condition of BiSb, we achieve a large effective spin Hall angle of 6.0 ± 0.1 and relatively high electrical conductivity of 1.5 × 105 Ω−1 m−1 at room temperature. We, then, demonstrate spin–orbit torque-induced magnetization switching driven by a small threshold current density of 1 × 106 Acm−2. Benchmarking shows that the writing power consumption of our stack is 2–3 orders smaller than that of heavy metals. [ABSTRACT FROM AUTHOR]

We used a micromagnetic model to study the head remanence of a perpendicular tapered main pole head. To reduce the head pole tip remanence, a single magnetic domain structure forming a vortex state from the pole tip to the tapered region is preferred. A tapered main pole structure with a trailing gap depth less than about 30 nm and a tapered angle (TGθ) equal to about 30° improved the writing efficiency. This was achieved with a head field value more than 1.3 times higher and with a head field gradient about 1.15 times higher than that of the conventional structure. Moreover, the pole tip remanence was reduced to a value closer to that of the conventional structure. The reduction in the throat height had less effect on the reduction in the head remanence in the tapered head than in the conventional head. We also discuss both single pole heads and shielded heads. [ABSTRACT FROM AUTHOR]