Low-resistance spin-dependent tunnel junctions with ZrAlOx barriers

Spin-dependent tunnel junctions with ZrAlOx barriers were formed by natural oxidation (5 min at 10 Torr) of 7-A-thick Zr–Al films. Resistance×area products of 6 Ω μm2 were achieved with a 15.3% tunnel magnetoresistance (TMR) signal. Bottom-pinned (MnIr) junctions were deposited on top of 600-A-thick, ion-beam-smoothed, low-resistance, Al electrodes. Effective average barrier height and thickness are 0.28 eV and 8.2 A, respectively, and breakdown voltage is 0.41 V for 1 μm2 junctions. The TMR signal decreases by half at a bias voltage of 210 mV. Junction TMR decreases for anneals above 250 °C. High-resolution transmission electron microscopy indicates that ZrAlOx forms an amorphous barrier that is smoother than pure crystalline ZrOx or pure amorphous AlOx barriers. These low-resistance tunnel junctions are attractive for read head applications above 100 Gbit/in.2 where competitive signal-to-noise ratios imply resistance×area products of few Ω μm2 and TMR signals near or above 20%.