Abstract
Spin-orbit torque has attracted considerable attention as a means to overcome limits of devices based on spin-transfer torque. However, a small magnetic field that is collinear to the current flow must be applied to break symmetry and induce deterministic current-induced magnetization switching. Recently, a junction utilizing interlayer coupling mediated by a Ru spacer layer between two CoFe layers was designed for symmetry breaking and exhibited current-induced magnetization switching without a magnetic field. Here, we demonstrate zero-field current-induced switching of the perpendicular magnetization of a Co layer that is indirectly coupled with a CoFe layer via a Ta spacer. The weak interlayer coupling exhibited by Ta allows the layer thickness to be relatively small (≈0.5 nm), enabling appropriate interlayer coupling to induce spin-orbit torque for current-induced magnetic switching. External magnetic field effects on switching characteristics show that the current switching process is quite stable against external environments.
Highlights
All data generated or analysed during this study are included in this published article
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Summary
Fabrication and magnetic properties of the sample. Figure 1(a) shows a scanning electron microscopy (SEM) image of a Hall bar with a magnetic multi-layer consisting of the following: Ta(3 nm)/Pt(5 nm)/ Co(0.6 nm)/Pt(0.4 nm)/Ta(0.5 nm)/CoFe(3 nm)/IrMn(15 nm)/Ta(1 nm). This change in the switching sequence indicates that the magnetic polarity of the CoFe layer is reversed by the applied field from the positive to the negative x-axis. The quantity of critical current density decreases with the positive field is relatively small (2~3×1010Am−2), compared to that of the critical current density increase observed with a negative field (5~6×1010Am−2), which indicates that the field that is antiparallel to the exchange coupling has a greater effect on the current-induced switching than the parallel field This change in the critical current density depending on the direction of the applied magnetic field can be understood in terms of the interlayer coupling between the Co and CoFe layers. Selecting the proper material for a spacer layer with an appropriate interlayer coupling strength holds great potential for both enhanced zero-field switching and optimizing junction functionality
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