Oxygen migration at the Fe/FeO x /Al and the Co/CoO x /Al interfaces, which are of importance for magnetic tunnel junctions, was investigated using Auger electron spectroscopy by chemical shift analysis. After depositing an Al film on the oxide surface, a reduction of the oxides by Al is observed. The oxygen atoms escaping from the electrodes migrate towards Al, forming Al 2 O 3 . The migration is thermally activated as confirmed by annealing experiments. The obtained results are used to explain the reported performance increase of magnetic tunnel junctions after annealing up to 470 K.
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