Current and Shot Noise in a Ferromagnetic Double Tunnel Junction with an Atomic Size Spacer

Abstract

Recent interest in electronic transport in magnetic systems of a nanometer size is stimulated by expected applications in electronic devices. There are also interesting physical phenomena due to the interplay of spin and charge degrees of freedom as well as due to correlation between conducting channels for electrons with opposite spin orientations [1]. We have studied a ferromagnetic single electron transistor (fSET) [2], which consists of a metallic grain connected through tunnel barriers to two ferromagnetic electrodes. The grain size is of the order of one nanometer, so the single electron charging energy E _c = e ²/2C and the interlevel spacing ΔE are larger than the thermal energy k _B T. We show that Coulomb correlations on the grain can lead to new effects, for instance to negative differential resistance (NDR). Correlations between currents of electrons with different spin orientations have a significant influence on the shot noise. We show that apart from a typical reduction of the zero-frequency power spectrum below the Poissonian value S ⁰ _I = 2^eI