Spin-Orbit Torque and Magnetic Damping in Tailored Ferromagnetic Bilayers

For practical use of spin-orbit torque (SOT) in magnetic memory applications, the writing current density must be reduced, not only for low power consumption and CMOS compatibility, but also for enhanced endurance and reliability. The authors study SOT-driven ferromagnetic resonance in ferromagnetic bilayers of cobalt and permalloy, sandwiched between Pt and MgO. Here the Pt/ferromagnet interface chiefly sets the spin Hall angle, but magnetic dissipation is also influenced by the ferromagnet/MgO interface. The configuration Pt/Co/Py/MgO seems to require less writing energy than Pt/Py/Co/MgO in SOT-driven magnetic switching.