Shot noise in magnetic tunnel junctions from first principles

We compute the shot noise in ballistic and disordered Fe|MgO|Fe tunnel junctions by a wave-function-matching method. For tunnel barriers with ?5 atomic layers we find a suppression of the Fano factor as a function of the magnetic configuration. In the antiparallel configuration the shot noise is full up to a threshold bias that indicates the onset of resonant tunneling. We find excellent agreement with recent experiments when interface disorder is taken into account