1 ∕ f noise in magnetic tunnel junctions with MgO tunnel barriers

Abstract

Electrical noise measurements are reported for magnetic tunnel junctions having magnesium oxide tunnel barriers. These junctions have resistance-area products (RAPs) of order 10–100MΩμm2 and exhibit zero-bias tunneling magnetoresistance ratios (TMRs) as high as 120% at room temperature. The TMR is bias dependent and decreases to half its maximum value for biases near 300 mV. The dominant low-frequency electrical noise is due to resistance fluctuations having a 1∕f-like power spectral dependence and a nonmagnetic origin. The normalized 1∕f noise parameter, α, is found to be of order 10−7 to 10−6 which compares favorably to magnetic tunnel junctions consisting of an aluminum oxide barrier with comparable RAPs but lower TMR. At high biases, α is found to decrease which we attribute to defect-assisted tunneling mechanisms.