  Spin Hall nano oscillators (SHNOs) are promising candidates for neuromorphic
computing due to their miniaturized dimensions, non-linearity, fast dynamics,
and ability to synchronize in long chains and arrays. However, tuning the
individual SHNOs in large chains/arrays, which is key to implementing synaptic
control, has remained a challenge. Here, we demonstrate circular memristive
nano-gates, both precisely aligned and shifted with respect to
nano-constriction SHNOs of W/CoFeB/HfOx, with increased quality of the device
tunability. Gating at the exact center of the nano-constriction region is found
to cause irreversible degradation to the oxide layer, resulting in a permanent
frequency shift of the auto-oscillating modes. As a remedy, gates shifted
outside of the immediate nano-constriction region can tune the frequency
dramatically (>200 MHz) without causing any permanent change to the
constriction region. Circular memristive nano-gates can, therefore, be used in
SHNO chains/arrays to manipulate the synchronization states precisely over
large networks of oscillators.
