Current and power spectrum in a magnetic tunnel device with an atomic-size spacer

Current and its noise in a ferromagnetic double tunnel barrier device with a small spacer particle were studied in the framework of the sequential tunneling approach. Analytical formulas were derived for electron tunneling through the spacer particle containing only a single energy level. It was shown that Coulomb interactions of electrons with a different spin orientation lead to an increase of the tunnel magnetoresistance. interactions can also be responsible for the negative differential resistance. A current noise study showed which relaxation processes can enhance or reduce fluctuations leading either to a super-Poissonian or a sub-Poissonian shot noise.