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A gate voltage application in a Si-based spin metal-oxide-semiconductor field-effect transistor (spin MOSFET) modulates spin accumulation voltages, where both electrical conductivity and drift velocity are modified while keeping constant electric current. An unprecedented reduction in the spin accumulation voltages in a Si spin MOSFET under negative gate voltage applications is observed in a high electric bias current regime. To support our claim, the electric bias current dependence of the spin accumulation voltage under the gate voltage applications is investigated in detail and compared with a spin drift diffusion model including the conductance mismatch effect. The drastic decrease in the mobility and spin lifetime in the Si channel is ascribable to the optical phonon emission at the high electric bias current, which consequently reduced the spin accumulation voltage. [ABSTRACT FROM AUTHOR]

In a perpendicular magnetic anisotropy (PMA) system, spin–orbit torque (SOT)-induced magnetization switching shows promise in terms of high speed and stability, but additional in-plane directional symmetry breaking is necessary to achieve deterministic switching. Here, we observed all-electric magnetization switching by SOT in a conventional heavy metal/ferromagnetic structure deposited on a 3.25° miscut sapphire substrate. To better understand the origin of field-free switching, we conducted azimuthal angle-dependent PMA analysis and found that the magnetic anisotropy is slightly tilted in the direction of the miscut step. Despite a few degrees of tilting angle (<3°), we also confirmed that a slant PMA is the origin of the field-free switching by micromagnetic simulations. [ABSTRACT FROM AUTHOR]

For deterministic magnetization switching by spin–orbit torque (SOT) in a perpendicular magnetic anisotropy system, an additional in-plane direction magnetic field is essential to break the lateral symmetry. Realizing chirality in a magnetic ordering system can be one approach for achieving asymmetry in the lateral direction for field-free magnetization switching. However, systematic analysis of the influence of the chiral spin system on deterministic switching is still scarce. We investigate the field-free SOT-induced magnetization switching by using a chiral spin configuration experimentally and theoretically with micromagnetic simulations. We designed a system in which only part of the ferromagnetic layer overlaps with the heavy metal layer in the Pt/Co/MgO structure. Therefore, a spin current exerts only on a local area of the ferromagnetic layer, which results in a Néel-type chiral spin configuration. The induced chiral spin configuration can be stabilized (or destabilized) depending on the sign of the interfacial Dzyaloshinskii–Moriya interaction and the direction of the current. The stabilized spin configuration plays a crucial role in the deterministic switching in the zero field. We expect our findings to widen the perspective on chirality-based all-electrical SOT device applications. [ABSTRACT FROM AUTHOR]