  Synchronization of large spin Hall nano-oscillators (SHNO) arrays is an
appealing approach toward ultra-fast non-conventional computing based on
nanoscale coupled oscillator networks. However, for large arrays, interfacing
to the network, tuning its individual oscillators, their coupling, and
providing built-in memory units for training purposes, remain substantial
challenges. Here, we address all these challenges using memristive gating of
W/CoFeB/MgO/AlOx based SHNOs. In its high resistance state (HRS), the memristor
modulates the perpendicular magnetic anisotropy (PMA) at the CoFeB/MgO
interface purely by the applied electric field. In its low resistance state
(LRS), and depending on the voltage polarity, the memristor adds/subtracts
current to/from the SHNO drive. The operation in both the HRS and LRS affects
the SHNO auto-oscillation mode and frequency, which can be tuned up to 28
MHz/V. This tuning allows us to reversibly turn on/off mutual synchronization
in chains of four SHNOs. We also demonstrate two individually controlled
memristors to tailor both the coupling strength and the frequency of the
synchronized state. Memristor gating is therefore an efficient approach to
input, tune, and store the state of the SHNO array for any non-conventional
computing paradigm, all in one platform.
