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

Current and its noise in a ferromagnetic double tunnel barrier device with a small spacer particle were studied in the framework of the sequential tun neling approach. Analytical formulas were derived for electron tunneling th rough the spacer particle containing only a single energy level. It was sho wn 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 s tudy showed which relaxation processes can enhance or reduce fluctuations l eading either to a super-Poissonian or a sub-Poissonian shot noise.