  A mechanism is advanced suggesting the resolution of the dichotomy of
long-lived spin polarization storage versus fast spin reversal at the required
time. A system of atoms or molecules is considered interacting through magnetic
dipolar forces. The constituents are assumed to possess internal structure
allowing for the generation of the alternating-current quadratic Zeeman effect,
whose characteristics can be efficiently regulated by quasiresonant dressing.
The sample is connected to an electric circuit producing a feedback field
acting on spins. By switching on and off the alternating-current quadratic
Zeeman effect it is possible to realize spin reversals with a required delay
time. The suggested technique of regulated spin reversal can be used in quantum
information processing and spintronics.
