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 (RxA<1 Ω μm2 and MR>20% for areal densities >200 Gb/in2). This letter shows that competitive low RxA junctions can be produced using underoxidized barriers starting from 0.9 nm thick Al layers. For as-deposited junctions, tunneling magnetoresistance (TMR) ∼20% for RxA∼2-15 Ω μm2 is obtained, while in the RxA∼60-150 Ω μm2 range, TMR values between 40% to 45% are achieved. A limited number of junctions exhibits considerably lower RxA values with respect to the average, while keeping a similar MR (down to 0.44 Ω μm2 with TMR of 20% and down to 2.2 Ω μm2 with TMR of 52%). Experimental data suggest that current confinement to small regions (barrier defects/hot spots) may explain these results