Spin torque oscillator based on magnetic tunnel junction with MgO cap layer for radio-frequency-oriented neuromorphic computing

Recently, it has been proposed that spin torque oscillators (STOs) and spin torque diodes could be used as artificial neurons and synapses to directly process microwave signals, which could lower latency and power consumption greatly. However, one critical challenge is to make the microwave emission frequency of the STO stay constant with a varying input current. In this work, we study the microwave emission characteristics of STOs based on magnetic tunnel junction with MgO cap layer. By applying a small magnetic field, we realize the invariability of the microwave emission frequency of the STO, making it qualified to act as artificial neuron. Furthermore, we have simulated an artificial neural network using STO neuron to recognize the handwritten digits in the Mixed National Institute of Standards and Technology database, and obtained a high accuracy of 92.28%. Our work paves the way for the development of radio-frequency-oriented neuromorphic computing systems.