Effects of temperature, deposition conditions, and magnetic field on Ni80Fe20/Fe50Mn50/Ni80Fe20/Al2O3/Co and Ni80Fe20/Al2O3/Co magnetic tunnel junctions

We fabricated magnetic tunnel junctions (MTJs) of Ni-80 Fe-20/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 230degreesC for 15 min after deposition. Low-temperature measurements revealed an increase injunction 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.