  Spin transfer torque magnetic random access memory (STT-MRAM) is a promising
candidate for next generation memory as it is non-volatile, fast, and has
unlimited endurance. Another important aspect of STT-MRAM is that its core
component, the nanoscale magnetic tunneling junction (MTJ), is thought to be
radiation hard, making it attractive for space and nuclear technology
applications. However, studies of the effects of high doses of ionizing
radiation on STT-MRAM writing process are lacking. Here we report measurements
of the impact of high doses of gamma and neutron radiation on nanoscale MTJs
with perpendicular magnetic anistropy used in STT-MRAM. We characterize the
tunneling magnetoresistance, the magnetic field switching, and the
current-induced switching before and after irradiation. Our results demonstrate
that all these key properties of nanoscale MTJs relevant to STT-MRAM
applications are robust against ionizing radiation. Additionally, we perform
experiments on thermally driven stochastic switching in the gamma ray
environment. These results indicate that nanoscale MTJs are promising building
blocks for radiation-hard non-von Neumann computing.
