In spontaneous Raman process in atomic cell at high gain, both the Stokes
field and the accompanying collective atomic excitation (atomic spin wave) are
coherent. We find that, due to the spontaneous nature of the process, the
phases of the Stokes field and the atomic spin wave change randomly from one
realization to another but are anti-correlated. The phases of the atomic
ensembles are read out via another Raman process at a later time, thus
realizing phase memory in atoms. The observation of phase correlation between
the Stokes field and the collective atomic excitations is an important step
towards macroscopic EPR-type entanglement of continuous variables between light
and atoms
