  The electric polarization hysteresis loops and remanent polarization were
revealed in multiferroics RMn$_2$O$_5$ with $R = Gd$ and $Bi$ at wide
temperature interval from 5 K up to 330 K. Until recently, the long-range
ferroelectric order having an exchange-striction magnetic nature had been
observed in RMn$_2$O$_5$ only at low temperatures ($T\leq T_C = 30$ -- 35 K).
We believe that the polarization we observed was caused by the frozen
superparaelectric state which was formed by the restricted polar domains
resulting from phase separation and charge carriers self-organization. At some
sufficiently high temperatures $T\gg T_C$ the frozen superparaelectric state
was destroyed, and the conventional superparaelectric state occurred. This
happened when the potential barriers of the restricted polar domain
reorientations become equal to the kinetic energy of the itinerant electrons
(leakage). The hysteresis loops were measured by the so-called PUND method
which allowed us to correctly subtract the contribution of conductivity from
the measured polarization. The correlations between properties of the phase
separation domains and polarization were revealed and studied. The
high-temperature polarization also had a magnetic nature and was controlled by
the magnetic field because the double exchange between pairs of Mn ions with
different valences (Mn$^{3+}$ and Mn$^{4+}$) in RMn$_2$O$_5$ was the basic
interaction resulting in phase separation.
