60% magnetoresistance at room temperature in Co–Fe/Al–O/Co–Fe tunnel junctions oxidized with Kr–O[sub 2] plasma

Tsunoda, Masakiyo; Nishikawa, Kazuhiro; Ogata, Satoshi; Takahashi, Migaku
April 2002
Applied Physics Letters;4/29/2002, Vol. 80 Issue 17, p3135
Academic Journal
The influence of the mixed inert gas species for plasma oxidization process of a metallic Al layer on the tunnel magnetoresistance (TMR) was investigated for a magnetic tunnel junction (MTJ), Ta 50 Å/Cu 200 Å/Ta 200 Å/Ni–Fe 50 Å/Cu 50 Å/Mn[sub 75]Ir[sub 25] 100 Å/Co[sub 70]Fe[sub 30] 25 Å/Al–O/Co[sub 70]Fe[sub 30] 25 Å/Ni–Fe 100 Å/Cu 200 Å/Ta 50 Å. Using Kr–O[sub 2] plasma, a 58.8% of TMR ratio was obtained at room temperature after annealing the junction at 300 °C, while the achieved TMR ratio of the MTJ fabricated with usual Ar–O[sub 2] plasma remained 48.6%. A faster oxidization rate of the Al layer by using Kr–O[sub 2] plasma is a possible cause to prevent the over oxidization of the Al layer, which depolarizes the surface of the underlaid ferromagnetic electrode, and to realize a large magnetoresistance. © 2002 American Institute of Physics.


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