Dynamics of a spin-polarized electron liquid: Spin oscillations with a low decay

We propose spintronic systems which spin dynamics is determined by the frequent normal electron collisions. Spin oscillation induced by the electrical field is predicted. The hydrodynamic equations for the electron spin-polarized liquid have been obtained and analyzed. We found that in the case of a conducting magnetic-inhomogeneous ring, both the spin polarization and the drift current may oscillate simultaneously with a large decay time ("spin pendulum"). We demonstrate also that the spin polarization of the electron density may be revealed via the voltage between the ends of the open circuit with an inhomogeneous spin polarization. The effect may be observed both in the hydrodynamic and the diffusive regimes.