Magnetoresistance effect of planar-type ferromagnetic tunnel junctions

摘要

Planar-type Ni/Ni oxide/Ni ferromagnetic tunnel junctions were fabricated by using nanolithography techniques. Ni oxide barriers were formed by scanning probe microscope local oxidation. For the observation of magnetoresistance (MR) difference across the junction, source and drain electrodes were patterned into different shapes by focused ion beam lithography, in order to induce magnetic shape anisotropy. The resistance of planar-type Ni/Ni oxide/Ni ferromagnetic tunnel junction was changed by applying a magnetic field, and MR ratio exhibited above 100 percent at 16.3 K. With increasing the bias voltage from 0.15 to 1.0 mV at 16.3 K, the MR ratio decreases from 103 percent to 5 percent. Furthermore, the MR ratio at 0.5 mV decreases from 8.5 percent to 0.2 percent with increasing the temperature from 16.3 to 200 K. This result implies that planar-type ferromagnetic tunnel junctions have potential use as nanoscale magnetoresistive elements.