Stochastic magnetic actuated random transducer devices based on perpendicular magnetic tunnel junctions

TL;DR

This paper demonstrates that perpendicular magnetic tunnel junctions can be used as fast, robust true random number generators in the ballistic regime, passing standard statistical tests and maintaining stable bit probabilities over time.

Contribution

It introduces a novel application of pMTJs as high-speed true random number generators that are more robust and environmentally stable than previous stochastic nanomagnetic devices.

Findings

Bitstreams follow binomial distribution

Can generate uniform 8-bit random numbers

Pass all NIST randomness tests with minimal processing

Abstract

True random number generators are of great interest in many computing applications such as cryptography, neuromorphic systems and Monte Carlo simulations. Here we investigate perpendicular magnetic tunnel junction nanopillars (pMTJs) activated by short duration (ns) pulses in the ballistic limit for such applications. In this limit, a pulse can transform the Boltzmann distribution of initial free layer magnetization states into randomly magnetized down or up states, i.e. a bit that is 0 or 1, easily determined by measurement of the junction's tunnel resistance. It is demonstrated that bitstreams with millions of events: 1) are very well described by the binomial distribution; 2) can be used to create a uniform distribution of 8-bit random numbers; 3) pass multiple statistical tests for true randomness, including all the National Institute of Standards tests for random number generators with only one XOR operation; and 4) can have no drift in the bit probability with time. The results presented here show that pMTJs operated in the ballistic regime can generate true random numbers at GHz bitrates, while being more robust to environmental changes, such as their operating temperature, compared to other stochastic nanomagnetic devices.