Low-resistance magnetic tunnel junctions prepared by partial remote plasma oxidation of 0.9 nm Al barriers

Current perpendicular to the plane read-head elements suitable for high-density magnetic storage require low resistance while maintaining a reasonable magnetoresistive (MR) signal (R x A < 1 Omega mu m(2) and MR > 20% for areal densities > 200 Gb/in(2)). This letter shows that competitive low R x A junctions can be produced using underoxidized barriers starting from 0.9 nm thick Al layers. For as-deposited junctions, tunneling magnetoresistance (TMR) similar to 20% for R x A similar to 2-15 Omega mu m(2) is obtained, while in the R x A similar to 60 - 150 Omega mu m(2) range, TMR values between 40% to 45% are achieved. A limited number of junctions exhibits considerably lower R x A values with respect to the average, while keeping a similar MR (down to 0.44 Omega mu m(2) with TMR of 20% and down to 2.2 Omega mu m(2) with TMR of 52%). Experimental data suggest that current confinement to small regions (barrier defects/hot spots) may explain these results. (c) 2005 American Institute of Physics.