Magnetization switching and deterministic nucleation in Co/Ni multilayered disks induced by spin-orbit torques

We present experimental and numerical results on the magnetization reversal induced by spin-orbit torques of micronic disks of a ferromagnetic multilayer with perpendicular magnetic anisotropy on top of a Pt track: Pt (6 nm)/[Co(0.2 nm)/Ni(0.6 nm)] x 5/Al(5 nm). The current induced magnetization switching process is probed by anomalous Hall effect measurements and Kerr microscopy. The electrical characterization reveals the critical current for the complete reversal to be about 3 x 10(11) A/m(2), and Kerr microscopy uncovers a deterministic nucleation that depends on current and field polarity. Through the use of experimental switching phase diagrams coupled to micromagnetic simulations, we evaluated the field-like to damping-like torque ratio to be 0.73 +/- 0.05, which is in good agreement with experimental values observed by second harmonic measurements. These measurements emphasize an unexpectedly large field-like contribution in this relatively thick Co/Ni multilayer (4 nm). In light of these experiments and simulations, we discuss the key parameters needed to understand the magnetization reversal, namely, the field and damping-like torques and the Dzyaloshinskii-Moriya interaction. Published under an exclusive license by AIP Publishing.

Automated summary

In this study, experimental and numerical results were presented to investigate the magnetization reversal induced by spin-orbit torques in micronic disks of a ferromagnetic multilayer. The critical current for complete reversal, as well as the torque ratio and nucleation process, were determined. The experiments and simulations provided insights into the key parameters involved in the magnetization reversal process.