Transport through quantum-dot spin valves containing magnetic impurities

We investigate transport through a single-level quantum dot coupled to noncollinearly magnetized ferromagnets in the presence of localized spins in either the tunnel barrier or on the quantum dot. For a spin embedded in the tunnel barrier, we find an interplay between current-induced switching of the spin, spin-dependent tunneling through the barrier and spin accumulation on the dot resulting in characteristic signals in the current. We, furthermore, find huge Fano factors due to random telegraph noise. For noncollinear geometries, an exchange field that depends on the impurity spin state leads to characteristic fingerprints in the transport properties. In the case of a spin on the quantum dot, we find that the frequency-dependent Fano factor can be used to study the nontrivial dynamics of the spins on the dot due to the interplay between exchange interaction and coupling to external and exchange magnetic fields.

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