  Random spin-exchange collisions in warm alkali vapor cause rapid decoherence
and act to equilibriate the spin state of the atoms. In contrast, here we
demonstrate experimentally and theoretically a coherent coupling of one alkali
specie to another specie, mediated by these random collisions. We show that,
the minor specie (potassium) inherits the magnetic properties of the dominant
specie (rubidium), including its lifetime (T1), coherence time (T2),
gyromagnetic ratio, and SERF magnetic-field threshold. We further show that
this coupling can be completely controlled by varying the strength of the
magnetic field. Finally, we explain these phenomena analytically by
modes-mixing of the two species via spin-exchange collisions.
