Electrically connected spin-torque oscillators array for 2.4GHz WiFi band transmission and energy harvesting

The mutual synchronization of spin-torque oscillators (STOs) is critical for communication, energy harvesting and neuromorphic applications. Short range magnetic coupling-based synchronization has spatial restrictions (few mu m), whereas the long-range electrical synchronization using vortex STOs has limited frequency responses in hundreds MHz (<500MHz), restricting them for on-chip GHz-range applications. Here, we demonstrate electrical synchronization of four non-vortex uniformly-magnetized STOs using a single common current source in both parallel and series configurations at 2.4GHz band, resolving the frequency-area quandary for designing STO based on-chip communication systems. Under injection locking, synchronized STOs demonstrate an excellent time-domain stability and substantially improved phase noise performance. By integrating the electrically connected eight STOs, we demonstrate the battery-free energy-harvesting system by utilizing the wireless radio-frequency energy to power electronic devices such as LEDs. Our results highlight the significance of electrical topology (series vs. parallel) while designing an on-chip STOs system. Spin torque oscillators (STOs) are attractive potential alternative for many high frequency applications, due to their small area and CMOS compatibility. Here, Sharma et al succeed in the electrical synchronization of four STOs, and use their setup to demonstrate wireless and battery-free energy harvesting using eight STOs.

Automated summary

This study demonstrates the electrical synchronization of four non-vortex uniformly-magnetized STOs using a single common current source in both parallel and series configurations, resolving the frequency-area quandary for designing on-chip communication systems based on STOs. Additionally, by integrating the electrically connected eight STOs, the researchers successfully demonstrate a wireless and battery-free energy harvesting system.