Shot noise in double barrier epitaxial magnetic tunnel junctions

Shot noise has been shown to be an effective tool to study statistics of electron tunnelling in single barrier magnetic tunnel junctions [1-2]. Here we report on shot noise and tunnelling magnetoresistance measurements in fully epitaxial Fe/MgO/Fe/MgO/Fe double barrier magnetic tunnel junctions. We observed that the shot noise is essentially determined by the barriers' symmetry and relative magnetic configuration. Enhanced barrier asymmetry effectively suppresses electron correlations, and the noise approaches the Poissonian limit. The proposed model of sequential tunnelling (with spin relaxation) through the magnetic layer inside the tunnel barrier satisfactory explains the experimental observations. [1] R.Guerrero, et al., Phys. Rev. Lett. 97, 0266602 (2006). [2] R.Guerrero, et al, Appl. Phys. Lett. 91, 132504 (2007).