Spin oscillation of a quantum dot embedded in a ferromagnetic ring with two interacting electrons

The spin oscillation of a quantum dot embedded in a ferromagnetic ring is investigated. We suppose that there are two electrons with an opposite spin in the system, which is a sort of excited state of the system that includes ferromagnetism. By numerically solving the time-dependent Schrödinger equations for the many-body states, the spin oscillations of a quantum dot are derived and studied in detail. It is found that the amplitude and frequency of the oscillations depend sensitively on the exchange energy of ferromagnetic lead, the coupling strength between the dot and ferromagnetic lead, the gate voltage, and Coulomb repulsion energy of quantum dot. We show also that the magnetic moment on the dot can be controlled by tuning the exchange field of ferromagnetic lead.