Interdiffusion and thermal stability in magnetic tunnel junction ferromagnet/insulator/ferromagnet trilayer structures

We used molecular beam epitaxy grown magnetic tunnel junction structures for thermal stability studies using x-ray photoelectron spectroscopy (XPS) and in situ scanning tunneling microscopy (STM). Unannealed trilayers show no oxidation of the bottom magnetic layer for barriers thicker than 1.1 nm. However, upon annealing, we find that the metallic XPS peak of the top layers decrease dramatically, while that of the bottom and barrier layers increases. STM images of the Co top layer on the Al–oxide barrier show that the Co does not agglomerate upon annealing up to 500 °C, which suggests interdiffusion is the most likely explanation for the XPS data.