Influence of Pinholes on MgO-Tunnel Junction Barrier Parameters Obtained from Current–Voltage Characteristics

Magnetic tunnel junctions (MTJs) with thin barriers are already used as read sensors in recording media. However, the presence of pinholes across such few Å thick barriers cannot be excluded and one needs to investigate their effect on the MTJ-transport properties. By applying large electrical currents we could change the electrical resistance of the studied MgO MTJs (due to pinhole-size variations), and study how pinholes influence the barrier parameters (thickness t and height ϕ) obtained by fitting current–voltage characteristics to Simmons' model. We found that, with decreasing resistance, the barrier thickness (height) decreases (increases). These results were well reproduced by a model of parallel-resistances, allowing us to estimate pinhole-free barrier parameters.