Room-temperature electric polarization induced by phase separation in multiferroic GdMn2O5
B. Kh. Khannanov, V. A. Sanina, E. I. Golovenchits, M. P. Scheglov
Ioffe Physical Technical Institute of the RAS, 194021 St. Petersburg, Russia
Abstract
It was generally accepted until recently that multiferroics
RMn2O5 crystallized in the centrosymmetric
Pbam space group and ferroelectricity in them could exist only at
low temperatures
due to the magnetic exchange striction. Recent comprehensive structural
studies
(Phys. Rev. Lett. 114, 117601 (2015)) have shown that the actual
symmetry of
RMn2O5 at room temperature is a noncentrosymmetric monoclinic
Pm sp. gr.,
which allows room temperature ferroelectricity to exist. However, such a
polarization has not yet been found.
Our electric polarization loop studies of GdMn2O5 have revealed
that a polarization
does exist up to room temperature. This polarization occurs mainly in
restricted polar domains
that arise in the initial GdMn2O5 matrix due to phase separation
and charge carrier self-organization.
These domains are self-consistent with the matrix, which leads to the
noncentrosymmetricity of the entire crystal.
The polarization is controlled by a magnetic field, thereby demonstrating
the presence of
magnetoelectric coupling. The low-temperature ferroelectricity enhances
the restricted
polar domain polarization along the b-axis.