Shot noise in low-resistance magnetic tunnel junctions

Shot noise measurements made on low-resistance magnetic tunnel junctions show results inconsistent with the resistance of the samples examined. The results yield lower than expected shot noise which is consistent with parallel path conduction (pinholes). A simple electrical model shows this should be true for noise measurements as well as for the tunneling magnetoresistance (TMR) as the resistance-area product (RxA) is reduced. The model suggests that a correlation between TMR and shot noise should exist assuming the presence of pinholes and that shot noise offers a useful experimental monitoring technique. The difficulties of making these measurements related to high frequency 1/f noise are discussed. Noise results are presented for high RxA and low RxA low-resistance samples which, in this particular case, both show the influence of pinhole shunting. (C) 2002 American Institute of Physics.