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

• Published in: Applied physics letters 2021-07, Vol.119 (3)
• Main Authors: Figueiredo-Prestes, N., Krishnia, S., Collin, S., Roussigné, Y., Belmeguenai, M., Chérif, S. M., Zarpellon, J., Mosca, D. H., Jaffrès, H., Vila, L., Reyren, N., George, J.-M.
• Format: Article
• Language: English
• Subjects: Aluminum; Applied physics; Cobalt; Condensed Matter; Critical current (superconductivity); Damping; Disks; Electrical properties; Ferromagnetism; Hall effect; Magnetic anisotropy; Magnetic switching; Magnetism; Magnetization reversal; Microscopy; Multilayers; Nickel; Nucleation; Other; Phase diagrams; Physics; Platinum; Torque
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/5.0050641

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)] × 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 × 10 11 A/m2, 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.