Interfacial capacitance effects in magnetic tunneling junctions

We have fabricated magnetic tunneling junctions by oxidizing a wedge-shaped aluminum layer to produce junctions with ideal oxidized as well as under and over oxidized junctions on a single wafer. By investigating the capacitance spectra, we are able to study the effects due to interface charge accumulation. The electron–electron interaction among accumulated interface charges leads to a voltage drop inside the magnetic electrodes, resulting in the measured capacitance differing from the geometric capacitance. We have extracted an interfacial capacitance of 16 μF/cm2 per interface and a screening length of 0.55 Å for FeNi electrodes.