Field-Free Spin-Orbit Torque Switching of Perpendicular Magnetization by Making Full Use of Spin Hall Effect

Field-free switching is a critical issue for spin-orbit torque-induced magnetic random-access memory (SOT-MRAM) with perpendicular magnetic anisotropic (PMA) towards application. If only the spin-polarized electrons along the y-direction (sigma(y)) are used, deterministic switching cannot be achieved, as the electron polarization direction and easy magnetization direction are orthogonal. In this work, z-direction polarized electrons (sigma(z)) produced by the spin Hall effect are utilized to provide the switching direction and sigma(y) provides the propulsion of magnetic reorientation. With the cooperation of sigma(y) and sigma(z) by the spin Hall effect, field-free switching is achieved. To combine with magnetic tunnel junction (MTJ), a model is proposed, in which heavy metals providing sigma(z) are deposited on MTJ with asymmetric writing line widths. This model retains the characteristics of read-write separation and realizes deterministic switching based on SOT.