Bipolar Random Spike and Bipolar Random Number Generation by Two Magnetic Tunnel Junctions

In several recent studies, the probabilistic nature of magnetic tunnel junction (MTJ) switching has been utilized rather than suppressed for proposals and demonstrations of specific or novel scenarios or applications, such as true random number generation, neural spike generation, stochastic computing (SC), and probabilistic spin logic. Among all schemes of operations for generating tunable random signals, dual-biasing is very simple but also robust against device variations. When an MTJ is connected to a voltage source with polarity encouraging parallel (P)-to-antiparallel (AP) switching by spin-transfer torque (STT), and under a static bias field that favors P-state, the MTJ can switch back and forth between two states randomly, due to the state-dependent modulation of current by the tunneling magnetoresistance (TMR) of the MTJ. In this work, we demonstrate bipolar random signal generation by connecting two MTJs in series with a voltage source.