Figure 4: Observation of the interface contribution.
From: Quantifying interface and bulk contributions to spin–orbit torque in magnetic bilayers
(a) Measured SOF and SOT coefficients in Ti(1)/CoFeB(0.7)/Cu(x)/Pt(5). The SOF coefficient shows an increase with very thin copper insertion and then decrease as the copper layer gets thicker, while the SOT coefficient shows a monotonic decay with increasing copper layer thickness. (b) The ratio between the SOF and SOT coefficients manifests two regimes as highlighted in the graph. In the green regime, where copper is thick enough to remove the interface effect between CoFeB and Pt, the βF/βT values are near 0.2. In the red regime, where the copper is too thin to form a continuous film, the βF/βT is lower, suggesting that there exists an interface effect that produces a SOF and SOT based on a different mechanism from the effect of the nonlocal spin current.
