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We fabricated magnetic tunnel junctions (MTJs) of Ni80Fe20/Fe50Mn50/Ni80Fe20/Al2O3/Co exchange-biased structures and Ni80Fe20/Al2O3/Co nonexchange-biased structures using shadow masks, with and without an in situ magnetic field. We magnetically annealed the junctions at 230°C for 15 min after deposition. Low-temperature measurements revealed an increase in junction resistance and tunneling magnetoresistance and enhancement of the exchange field for exchange-biased junctions. Post-deposition magnetic annealing at an optimum predicted temperature did not improve the quality of the Al2O3 but instead degraded it, highlighting the importance of other contributing factors. MTJs fabricated with an in situ magnetic field without any post-deposition magnetic annealing produced the most desirable results from the perspective of magnetic application technology.
Date of Publication: Jan. 2005