Magnetic field dependent noise in magnetic tunnel junction.

The measurements of voltage fluctuations at room temperature are performed for magnetic tunnel junction, patterned by photolithography to have 20 × 10 µm² in junction area. The observed noise power follows 1/f behavior for the whole applied magnetic field (H) range (-30 Oe≤H ≤30 Oe) and shows strong field dependence. The sharp increase in noise power spectral density is observed near a transition region from antiparallel to parallel magnetic state in two electrodes during field ramping down. In addition, the reduction of noise power density is accompanied by the reduction of magnetoresistance ratio after thermal annealing at 300°C for 700 s in the same junction. It is conjectured that the observed reduction of the noise level in our junction is due mainly to magnetic origin, such as thermally activated domain wall motion, rather than electrical origin. [ABSTRACT FROM AUTHOR]