Spin Torque Oscillators: The research at the heart of this effort is to better understand and control mutual synchronization of arrays of spintronic nanoscale oscillators operating in the range of 10 GHz to 40 GHz. The devices under study are well suited to neuromorphic applications because they are intrinsically nonlinear and strongly interact with high-frequency injected signals. Because of these properties they can, under certain circumstances, be frequency-locked together, although their relative phase can be changed. This makes these nanoscale (50 nm to 75 nm) devices excellent candidates for implementation in approximate computing architectures that have been developed over the last half-decade. NIST researchers are presently working on this approach in two-terminal “spin-transfer torque” oscillators and three-terminal “spin-orbit torque” oscillators. The goal is to understand how the oscillators can be most efficiently coupled together, either through spinwaves, magnetic fields, or electrical currents.
Magnetic Josephson Junction Devices: The focus of this research is to develop magnetic Josephson junctions (MJJs) as both synaptic and neuronal elements for neuromorphic circuitry. Josephson junctions intrinsically operate at frequencies of 100 GHz or more, meaning that they operate much faster than modern-day semiconductor devices and therefore can potentially perform computations at much higher speeds. Researchers in the Spin Electronics Group are developing essential components of an energy-efficient neuromorphic processor and have demonstrated a new form of an artificial synapse based on their newly developed MJJ barriers. Like the brain, these devices communicate via voltage spikes, but with zeptojoule pulse energies instead of the brain’s femtojoule pulse energies. The present research in the group is focused on how to couple these artificial synapses and neurons together.