Dynamics of Two Overlapping Spin Ensembles Interacting by Spin Exchange

We describe linear and nonlinear dynamics of spin-polarized K and [Formula presented] ensembles interacting by spin exchange. The interactions are dominated by the imaginary part of the spin-exchange cross section and each spin species is primarily affected by the average magnetization of the other. Operating in a very low magnetic field we demonstrate novel dynamics when the electron and nuclear spin precession frequencies are nearly matched. We observe transverse damping as well as a dynamic instability of the [Formula presented] spins interacting with polarized K vapor. We also demonstrate operation as a self-compensating comagnetometer, useful for tests of [Formula presented] violation and other precision measurements.