Ultrafast spin-orbit torque-induced magnetization switching in a 75°-canted magnetic tunnel junction

We investigate the switching dynamics of a 75 degrees-canted Spin-orbit torque (SOT) device with an in-plane easy axis using the micro-magnetic simulation. The switching time (tau) is evaluated from the time evolution of the magnetization. The device with a strong out-of-plane magnetic anisotropy (mu H-0(k)eff = -0.08 T) shows tau = 0.19 ns while a device with a strong in-plane magnetic anisotropy (mu H-0(k)eff = -0.9 T) shows tau = 0.32 ns. The increase of the damping constant (alpha) results in the increase of tau for both devices and the sub-nanosecond switching could be retained as alpha < 0.14 in the device with mu H-0(k)eff = -0.08 T, while this was achieved as alpha < 0.04 in the device with mu H-0(k)eff = -0.9 T. Furthermore when the field-like coefficient (beta) is increased, it leads to a decrease in tau, which can be reduced to 0.03 ns by increasing beta to 1 in the device with mu H-0(k)eff = -0.08 T. In order to achieve the same result in the device with mu H-0(k)eff = -0.9 T, beta must be increased to 6. These results indicate a way to achieve ultrafast field-free SOT switching of a few tens of picoseconds in nanometer-sized magnetic tunnel junction (MTJ) devices.