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

Electrical noise measurements are reported for magnetic tunnel junctions having magnesium oxide tunnel barriers. These junctions have resistance-area products (RAPs) of order 10-100 M Omega mu m(2) 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, alpha, 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, alpha is found to decrease which we attribute to defect-assisted tunneling mechanisms. (C) 2006 American Institute of Physics.