Voltage-driven gigahertz frequency tuning of spin Hall nano-oscillators

Abstract

Spin Hall nano-oscillators (SHNOs) exploiting current-driven magnetization auto-oscillation have recently received much attention because of their potential for neuromorphic computing. Widespread applications of neuromorphic devices with SHNOs require an energy-efficient method of tuning oscillation frequency over broad ranges and storing trained frequencies in SHNOs without the need for additional memory circuitry. While the voltage-driven frequency tuning of SHNOs has been demonstrated, it was volatile and limited to megahertz ranges. Here, we show that the frequency of SHNOs is controlled up to 2.1 GHz by an electric field of 1.25 MV/cm. The large frequency tuning is attributed to the voltage-controlled magnetic anisotropy (VCMA) in a perpendicularly magnetized Ta/Pt/[Co/Ni]n/Co/AlOx structure. Moreover, the non-volatile VCMA effect enables cumulative control of the frequency using repetitive voltage pulses which mimic the potentiation and depression functions of biological synapses. Our results suggest that the voltage-driven frequency tuning of SHNOs facilitates the development of energy-efficient neuromorphic devices.

Spin wave-driven variable-phase mutual synchronization in spin Hall nano-oscillators

“…Multiple novel mechanisms have been explored to generate and amplify PSWs [14,15], such as current induced spin-transfer torque (STT) [16][17][18] and spin-orbit torque (SOT) [19][20][21][22][23]. Nano-constriction spin Hall nano-oscillators (SHNOs) with perpendicular magnetic anisotropy (PMA) [24,25] are a particularly promising approach, as they are easy to fabricate [26,27], CMOS compatible [28], strongly voltage tunable [29][30][31][32], and known for their superior mutual synchronization at various length scales and dimensions [33][34][35].…”

Voltage-controlled magnetic anisotropy-based spintronic devices for magnetic memory applications: Challenges and perspectives

“…[69][70][71] As a result, the current that passes through the thin insulating barrier is extremely minimal, enhancing the energy efficiency of VCMA and making it appealing for a wide range of applications, such as MRAMs, 72,73 random number (RN) generators, [74][75][76] physically unclonable functions (PUFs), [77][78][79] neuromorphic computing, 80,81 and spintronic oscillators. [82][83][84][85][86][87] In this article, our primary focus is the VCMA-MRAM, which is discussed in Secs. II and III.…”

Robust Mutual Synchronization in Long Spin Hall Nano-oscillator Chains

“…The mutual synchronization of these oscillators in a chain can be explored for bioinspired computing and beyond ,, where each oscillator behaves as a neuron. Combined with voltage ,, and/or memristive control of synchronization (synaptic weights), these large chains can be used to locally or globally control the coupling between oscillators (neurons). The present work also serves as a stepping stone in the direction toward further scaling mutual synchronization to much larger square or rectangular arrays well beyond the previously demonstrated 64 oscillators.…”