Ferromagnetic tunnel junctions , Ta/Ni80Fe20/Cu/Ni80Fe20/IrMn/Co75Fe25/Al-oxide/Co75Fe25/Ni80Fe20/Ta, were fabricated using ICP oxidation, and the detailed annealing temperature dependence of the TMR effect was investigated. Thickness of the Al layer was varied from 6.6 to 7.7 Å before oxidation, and the oxidation time was optimized for each thickness. The 1-μm2 junctions were micro fabricated usinge-beam lithography. When the Al thickness was 6.6 Å, the RA decreased to 60-100 Ω·μm2 and the TMR ratio became 30%. The lower the RA was, the lower the TMR ratio became.
