  Magnetic tunnel junctions operating in the superparamagnetic regime are
promising devices in the field of probabilistic computing, which is suitable
for applications like high-dimensional optimization or sampling problems.
Further, random number generation is of interest in the field of cryptography.
For such applications, a device's uncorrelated fluctuation time-scale can
determine the effective system speed. It has been theoretically proposed that a
magnetic tunnel junction designed to have only easy-plane anisotropy provides
fluctuation rates determined by its easy-plane anisotropy field, and can
perform on nanosecond or faster time-scale as measured by its
magnetoresistance's autocorrelation in time. Here we provide experimental
evidence of nanosecond scale fluctuations in a circular shaped easy-plane
magnetic tunnel junction, consistent with finite-temperature coupled macrospin
simulation results and prior theoretical expectations. We further assess the
degree of stochasticity of such signal.
