Current fluctuations of noncollinear single-electron spin-valve transistors

We theoretically investigate the finite-frequency as well as the zero-frequency charge-current fluctuations through a noncollinear single-electron spin-valve transistor in the limit of sequential tunneling. The system under consideration consists of two tunnel junctions that connect a small central metallic island to two ferromagnetic leads with noncollinear magnetization. Due to the spin-dependent tunnel coupling and the electron-electron interaction on the central electrode an exchange field that acts on the accumulated island spin is present. We analyze how this many-particle interaction effect influences the current noise. In detail, we present that the field leads to a reduction of the sub-Poissonian Fano factor.