Magnetic-field-induced polarization and depolarization in $\mathrm{Ho}{\mathrm{Mn}}_2{\mathrm{O}}_5$ and $\mathrm{Er}{\mathrm{Mn}}_2{\mathrm{O}}_5$

The effects of the magnetic field $\left(H\right)$ on dielectric properties have been investigated for $R{\mathrm{Mn}}_2{\mathrm{O}}_5$ ($R=\mathrm{Ho}$ and Er), which undergo a transition to a ferroelectric state around $35\mathrm{K}$. With further decreasing temperature $\left(T\right)$, $\mathrm{Ho}{\mathrm{Mn}}_2{\mathrm{O}}_5$ shows the second dielectric transition to the lowest-$T$ phase (X), where spontaneous polarization is almost zero. The application of $H$ stabilizes the ferroelectric phase in $\mathrm{Ho}{\mathrm{Mn}}_2{\mathrm{O}}_5$, while the X phase in $\mathrm{Er}{\mathrm{Mn}}_2{\mathrm{O}}_5$ as the ground state. Accordingly, the electric polarization can be induced or extinguished by $H$, accompanying the hysteresis. Phase diagrams of these compounds have been established in the plane of $T$ vs $H$.