We demonstrate that shot noise in $\mathrm{Fe}/\mathrm{MgO}/\mathrm{Fe}/\mathrm{MgO}/\mathrm{Fe}$ double-barrier magnetic tunnel junctions is determined by the relative magnetic configuration of the junction and also by the asymmetry of the barriers. The proposed theoretical model, based on sequential tunneling through the system and including spin relaxation, successfully accounts for the experimental observations for bias voltages below 0.5 V, where the influence of quantum well states is negligible. A weak enhancement of conductance and shot noise, observed at some voltages (especially above 0.5 V), indicates the formation of quantum well states in the middle magnetic layer. The observed results open up new perspectives for a reliable magnetic control of the most fundamental noise in spintronic structures.

• Received 27 March 2012

DOI:https://doi.org/10.1103/PhysRevLett.109.066601