Low-frequency noise in MgO magnetic tunnel junctions

Abstract

Noise measurements have been performed in MgO-based tunnel junctions with normalized resistance in the range of 105–107Ωμm2 and various magnetoresistance ratios were investigated. Noise measurements in the frequency range of 1–1000Hz shows magnetically dependent pure 1∕f power spectra at low frequency. The 1∕f noise scales with bias voltage, indicating that the 1∕f noise can be attributed to magnetic tunnel junction resistance fluctuations. Bias voltage dependence of random telegraph noise (RTN) was observed, indicating electronic origin due to the charge-trapping mechanism. In the presence of the easy-axis bias field, our data exhibit a magnetic-field dependence of RTN that originates from magnetization fluctuations. A phenomenological noise parameter, defined for the comparison of noise levels in different junctions, was shown to be independent of the junction resistance-area product in the range investigated. This observation suggests that the decrease in tunnel resistance does not play an important role in reducing 1∕f noise.