Spin-dependent tunneling junctions with Fe55Ni45 electrodes and in situ resistive measurement of oxide growth

We have fabricated Si/Ta/Fe55Ni45/FeMn/Fe55Ni45/Al2O3/Fe55Ni45/Ta spin-dependent tunneling junctions, in which the tunneling barrier is formed by plasma oxidation. The as-deposited Fe55Ni45/FeMn bilayer has a surface exchange energy of 0.13 erg/cm2. A maximum tunneling magnetoresistive ratio of 16.5% is obtained in the junctions. We also developed an in situ resistance measurement technique to monitor tunneling barrier thickness during plasma oxidation. The plasma oxidation data are fitted to an oxide growth model based on cation hopping current and sputtering.