Fig. 4: Spin-orbit torque driven skyrmion motion.
From: Driving skyrmions in flow regime in synthetic ferrimagnets
a–d Current induced skyrmion motion in [Pt (3 nm)/Co (1.3 nm)/Tb (0.6 nm)/Al (3 nm)]×5 multilayers after application of two successive 10 ns wide current pulses in between two images with \(J=3.5\times {10}^{11}\) A/m2 under an external perpendicular field ~41 mT. The circles and the dashed lines are guide to eye to track the motion of individual skyrmions. e Average skyrmion velocity (filled symbols) vs current density for different samples with varying Tb thickness (red: Tb 0.25 nm, green: Tb 0.4 nm, blue: Tb 0.6 nm) in the multilayers. Error bars corresponding to each data points represent the standard deviation of the skyrmion velocity inside the tracks. The blue straight and dashed lines are reported from Fig. 3, and correspond to the fit of depinning law and the prediction for the flow regime, respectively. The green and red lines are guides to eye underlying the depinning law.
