Interfacial current-induced torques in Pt/Co/GdOx

Abstract

Current-driven domain wall (DW) motion is investigated in Pt/Co/GdOx nanostrips with perpendicular magnetic anisotropy. Measurements of the propagation field and the energy barrier for thermally activated DW motion reveal a large current-induced torque equivalent to an out-of-plane magnetic field of ~60 Oe per 10 11 A/m 2 . This same field-to-current scaling is shown to hold in both the slow thermally activated and fast near-flow regimes of DW motion.The current-induced torque decreases with 4 Å of Pt decorating the Co/GdOx interface and vanishes entirely with Pt replacing GdOx, suggesting that the Co/GdOx interface contributes directly to highly efficient current-driven DW motion.

Enhanced spin-orbit torques in Pt/Co/Ta heterostructures

“…Current-induced torques in ultrathin ferromagnets sandwiched by a heavy metal and an oxide have been of significant recent interest for highly efficient magnetization switching [1][2][3][4][5][6][7][8] and domain wall motion. [9][10][11][12][13][14] In these systems, strong spinorbit torques (SOTs) can arise through the spin Hall effect (SHE) [2][3][4]13,[15][16][17][18][19] and the Rashba effect 11,[20][21][22][23] at the heavymetal/ferromagnet interface, which can be exploited for lowpower operation of spintronic memory and logic devices. These effects produce both a Slonczewski-like torque [24][25][26] that drives magnetization switching, and a field-like torque 27 whose effective field lies parallel to the interface and orthogonal to the current flow direction.…”

Current-driven domain wall motion along high perpendicular anisotropy multilayers: The role of the Rashba field, the spin Hall effect, and the Dzyaloshinskii-Moriya interaction

“…The current-induced domain wall motion (CIDWM) along thin ferromagnetic layers with high perpendicular magnetoscrystalline anisotropy sandwiched between a heavy metal and an oxide has been demonstrated to be very efficient, [1][2][3][4] and it promises unprecedented opportunities for developing spintronic devices. 5 Apart from its technological interest, the CIDWM along these asymmetric stacks is also of fundamental relevance because it is related to interesting physics phenomena.…”

Assessment of Rashba Field Effects in Ultrathin Pt/Co/GdOx Submicrometer Strips

“…The uncertainty of this measurement yields an upper limit T/(10 A/m ), significantly lower than reported in [8]. We also analyze DW motion driven by field and current [2] and find no evidence of the Rashba effect suppressing the precessional mode of motion.…”

“…The velocities of DWs, driven by combinations of applied out-of-plane field and injected current, were measured using the time-resolved MOKE technique described in detail in [2] and [15]. DWs were initialized by the Oersted field from a 25-ns current pulse ( mA) injected through the Cu line orthogonal to the Pt/Co/GdOx strip as illustrated in Fig.…”

“…Out-of-plane magnetized thin films with strong perpendicular magnetic anisotropy are promising platforms for such devices, because of the narrow widths and lower threshold current densities for motion of DWs in these material systems. Recently, highly efficient currentdriven DW motion has been observed in out-of-plane magnetized trilayer structures consisting of an ultrathin ( nm) ferromagnetic Co layer embedded between a heavy-metal Pt underlayer and an oxide overlayer such as AlOx [1] or GdOx [2], with maximum DW velocities exceeding 100 m/s. The conventional adiabatic and nonadiabatic spin transfer torques (STTs) [3] cannot account for the high efficiencies or the current polarity-dependence of DW motion, which occurs in the direction opposing electron flow, in these Pt/Co/oxide strips.…”