Switching Dynamics of In-Plane Magnetized Spin-Orbit Torque Devices

In-plane magnetized spin-orbit torque (SOT) devices offer the possibility of low energy memory applications by utilizing the spin Hall effect in a heavy metal write lead for efficient spin torque switching of the bistable ferromagnetic element. One challenge is the optimization of the switching dynamics despite spatial variation of the internal magnetic field of the memory element, its magnetization and the write current. In turn this introduces a spatially dependent torque from the spin accumulation at the ferromagnet-heavy metal interface, and from the Oersted magnetic field associated with the write current pulse. The combination of spatial and temporal variations within an individual element can lead to complicated switching dynamics via formation of spin textures for very fast write pulses, which can slow the complete switching. In this work we use a combination of time-resolved magneto-optical microscopy and micromagnetic simulations to explore the requirements for optimal switching. This work provides additional insight for the most efficient operation of SOT memory elements by directly probing the dynamic magnetization with sub-micron resolution on picosecond timescales.