Low resistance spin-dependent tunnel junctions with ZrAlOx barriers

Abstract

Spin-dependent tunnel junctions with ZrAlOx barriers were fabricated with low resistance×area product 4 Ω×μm2, and tunnel magnetoresistance of 15.2%. Barrier fabrication was done by natural oxidation (5 min, at oxidation pressures ranging from 0.5 to 10 Torr). The junctions were deposited on top of 600 Å thick, ion beam smoothed, low resistance, Al electrodes. X-ray photoelectron spectroscopy analysis indicates the presence of AlOx, ZrO2, some remnant metallic Zr, but no metallic Al in the as-deposited barriers. 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/in2 where competitive signal to noise ratios imply resistance×area product below a few Ω×μm2, and tunneling magnetoresonance signals near or above 20%.