The exchange-biased electrode of magnetic tunneling junctions with under- and overoxidized AlO_(x) insulator layers were annealed at 300℃ to study the extent of the Mn diffusion. A significant amount of Mn diffusion into the AlO_(x) layer was observed in the overoxidized junction sample from Auger electron spectroscopy and the extent of Mn diffusion increased with increasing oxidation time. X-ray photoelectron spectroscopy (XPS) proved that Mn found at the CoFe/AlO_(x) interface in the overoxidized junction sample was in the form of Mn oxide. The XPS data suggest that the Mn diffusion was accelerated by the preferential oxidation of Mn at the CoFe/AlO_(x) interface.
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