Spin glass transition in a thin-film NiO/Permalloy bilayer

We experimentally study magnetization aging in a thin-film NiO/Permalloy bilayer. Aging characteristics are nearly independent of temperature below the exchange bias blocking temperature, but rapidly vary above it. The dependence on the magnetic history qualitatively changes across this temperature. The observed behaviors are consistent with the spin glass transition at the exchange bias blocking temperature, with significant implications for magnetism and magnetoelectronic phenomena in antiferromagnet/ferromagnet bilayers.