Breakdown behavior of current perpendicular to the plane devices with nano-oxide current screening layers

The resistance R and magneto-resistance (dR/R) changes of current perpendicular to the plane (CPP) pillars with nano-oxide current screening layers under constant voltage stress are measured. The pillars, with diameter ranging from 50 nm to 4 μm, are antiparallel pinned PtMn spin-valves and the CoFe nano-oxide layer is located in the Cu spacer layer. Results show that an irreversible damage occurs at 170 mV and at this voltage, both the resistance and magneto-resistance decrease. This indicates that pinhole formation and growth in the nano-oxide layer is responsible for the breakdown. As device sizes decrease, breakdown voltages increase from ∼40 mV up to ∼170 mV. This indicates that pinhole formation follows a weakest link model for the larger devices and is induced by reaching a critical current density (voltage) for the smaller devices.