Noise properties of magnetic and nonmagnetic tunnel junctions

Low-frequency voltage fluctuations in magnetic and nonmagnetic tunnel junctions have been investigated. Tunneling magnetoresistance ratio of junctions ranged from 8.6% to 50% at room temperature. The origin of voltage noise was observed to be nonmagnetic. It was found that the resistance fluctuations lead to 1/f noise at room temperature, whereas the white noise was dominant at 77 K. A phenomenological noise parameter, defined for the comparison of noise levels in different junctions, was shown to scale with the junction resistance–area product. This observation suggests that low values of resistance×area are required for a low noise operation as well as for the integration of magnetic tunnel junctions.